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RESEARCH LIBRARY 
Ore GebTY RESEARCH INSTITUTE 


JOHN MOORE ANDREAS COLOR CHEMISTRY LIBRARY FOUNDATION 








A SHORT MANUAL 
OF 


ANALYTICAL CHEMISTRY. 





; male oi f ery TORE 


De 


Pr 


- 


A SHORT MANUAL 


OF 


ANALYTICAL CHEMISTRY, 


Qualitative and Quantitatibe—Guorgunic und Organic. 


ARRANGED ON THE PRINCIPLE OF THE COURSE OF INSTRUCTION GIVEN AT THE 


peur LONDON SCHOOL OF PHARMACY. 


BY 


JOHN MUTER,’ a, PHD. FRSE, FLC, FCS, 


ANALYST TO THE METROPOLITAN ASYLUMS BOARD ; 

PUBLIC ANALYST FOR LAMBETH, WANDSWORTH, SOUTHWARK, NEWINGTON, ROTHERHITHE, AND 

THE LINDSEY DIVISION OF LINCOLNSHIRE } 

PAST PRESIDENT OF THE SOCIETY OF PUBLIC ANALYSTS} 

AUTHOR OF “ PHARMACEUTICAL AND MEDICAL CHEMISTRY” (THEORETICAL AND DESCRIPTIVE), 

““A KEY TO ORGANIC MATERIA MEDICA,” 

LATE EDITOR OF ‘‘ THE ANALYST,” 
ETC., ETC. 


FIRST AMERICAN FROM THE FOURTH ENGLISH EDITION, 


EDITED BY 


CLAUDE C. HAMILTON, ™.., rue. 


PROFESSOR OF ANALYTICAL CHEMISTRY IN THE UNIVERSITY MEDICAL COLLEGE AND 
THE KANSAS CITY COLLEGE OF PHARMACY 3 
PROFESSOR OF CHEMISTRY IN THE WESTERN DENTAL COLLEGE OF KANSAS CITY, MISSOURI. 


PHILADELPHIA: ‘ 
PUBLISHED BY 
P. BLAKISTON, SON, AND CO,, 
1012, WALNUT STREET. 
1891. 


THE GETTY RESEARCH 
INSTITUTE LIBRARY 

















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PeerACE TO THE AMERICAN EDITION. 


In this edition it has been the effort of the reviser to let the original text 
remain as little altered as circumstances would admit. Changes have been 
made only so far as the United States Pharmacopoeia made it compulsory 
to do so, excepting the chapter on urine analysis, which has been enlarged 
and illustrated and cuts of microscopic urinary sediments added. The name 
of each chemical formula has been introduced where the formula occurs. 
for the first time. This is done for the convenience of students of medical 
and pharmaceutical colleges, as well as for those who continue the application 
of analytical chemistry in their professional life. The processes for detection 
of certain acid radicals in presence of others are classified together, to be 
more applicable in searching for adulterations, as well as to save the student 
confusion by bringing the tests for radicals more closely together. A brief 
outline will be found on p. 61 which will aid the student materially in finding 
the pages required for the full analysis of a simple salt, and another, facing 
p. 64, for the analysis of mixed salts. A short list of tests for certain organic 
compounds has been added on p. 88. The chapter on water analysis has 
been altered to correspond with Wanklyn’s methods, as those are most 
generally used in America. Several other processes have been added, 
such as estimation of fat in milk, quantitative estimation of various ingre- 
dients of urine, estimation of chloral hydrate, etc. 

In conclusion, the reviser trusts that the changes made will find favor 
among the teachers and members of the profession in America, and that 
the present edition will find as many friends as former ones have found 


in the past. 
Cask i. 


UNIv. Mep. Cou. AND K. C. COLLEGE OF PHARMACY, © 
KANSAS CiTy, N.W. 


Fune 1891. 





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TApLEs OF CONTENTS. 


—~> a 


PART I.—QUALITATIVE ANALYSIS. 


CHAPTER I. 


The Processes Employed by Practical Chemists. 


; PAGE PAGE 
1. Solution . I 8. Fusion ; 4 
2. Lixiviation and Extraction . 2 g. Evaporation : 5 
3. Precipitation 2 | 10. Crystallisation and Dialysis 5 
4. Decantation 3 | 1. Electrolysis 6 
5. Filtration 3 | 12. Pyrology . 7 

6. Distillation . 4 | 13. Preparation of sulphuretted hy- 
7. Sublimation 4 drogen i 9 

CHAPTER II. 
Detection of the Metals. 
Group Reagents IO-I1 Division A. 18-21 
x I. Iron 18 
RUE ws Oe: 2. Cerium, 20 
I. Silver II 3. Aluminium 20 
2. Mercurosum . 12 4. Chromium 21 
3. Lead ed Division B. 21-24 
rouP II. 12-18 I. Manganese 21 
G 3 zi 
Division A. : ri-15 a Sane 22 
1. Mercuricum . 13 3: hee as 
2. Bismuth 14 = 3 
3. Copper . 14 | GRouP IV. 24-26 
4. Cadmium Is I. aN! . 24 
Aagiey 2. otrontium 25 
OEY An 3. Calcium 25 
oe Antimony 16 | GRoup V. : 26-28 
3, Tin 17 1. Magnesium 26 
4. Gold 17 = eee pf 
‘ 3. Potassium 

5. Platinum 18 7. Soditite 29 
Group III. 18-24 5. Ammoniuin EY Al 





Vili 


TABLE OF CONTENTS. 





CHAPTER III. 


Detection and Separation of Acidulous Radicals. 


. Hydrofluoric Acid and Fluorides 


2. Chlorine, eee Acid, and | 


Chlorides 


- Hypochlorites 

. Chlorates 

. Perchlorates 

. Bromine, Hydrobromic Acid, and 


Bre miides J 


. Hypobromites 
. Bromates . 
. Iodine, Hydriodic Acid, and lo- 


dides . 


. Iodates 
. Periodates . : : 
. Water and Hydrates . 
. Oxides 

. Sulphur, 


Hyd rosulphuri ric ‘Acid, 
and Sulphides 


. Thiosulphates (Hyposulphates) , 
. Sulphurous Acid and Sulphites . 
. Sulphuric Acid and Sulphates 

. Carbon, Carbonic Acid, and Car- 


boustes 


. Boric Acid and orates : 
. Silicic Acid and Silicates . i 
. Hydrofluosilicie Acid . : 

. Nitrous Acid and Nitrites . 

. Nitric Acid and Nitrates 

. Cyanogen, 


Hydrocyanic ‘Acid, 


and Cyanides 


. Cyanic Acid and Cyanates, ( Cyan- 


uric Acid, and Fulminic Acid 


; Thiocyanates Sabra oa) 

. Ferrocyanides 

. Ferricyanides 

- Hypophosphites . : 

. Phosphorous Acid and Phos- 


phites . 


. Meta-and Pyro-Phosphoric Acids 


and their Salts 


. Orthophosphoric Acid (B.P. I ay) and 


Orthophosphates . 


. Arsenious Acid and Arsenites 
. Arsenic Acid and Arseniates 
. Manganates ; 

. Permanganates . 

. Chromic Acid and Chromates 
. Stannic Acid 


and Stannates 
(Stannites ?) 


. Antimonic Acid . 

. Formic Acid and Formates 

. Acetic Acid and Acetates . ‘ 
. Valerianic Acid and Valerianates 
. Sulphovinates (Ethyl sulphates) 
. Stearic Acid and Stearates 

. Oleic Acid and Oleates 

. Lactic Acid and Lactates 

. Oxalic Acid and Oxalates , 

. Succinic Acid and Succinates 

. Malic Acid and Malates 

. Tartaric Acid and Tartrates 


. Citric Acid and Citrates 
. Meconic Acid and Meconates . 
. Carbolic Acid (or Phenol) and 


Carbolates (Phenates) . 


. Benzoic Acid and Benzoates 
. Salicylic Acid 


. Tannic, Gallic, and Pyrogallic 
Acid : ? 
. Separation of Chlorates and 


Chlorides 


. Detection of Chlorides in he 


presence of Bromides . 


. Detection of Bromides in the 


presence of Iodides 


. Detection of Chlorides in the 


presence of Iodides 


. Separation of Iodide from a Bro- 


mide and Chloride 


. Detection of an Iodate in an 


Iodide . 


. Detection of Soluble Sulphide i in 


the presence of Sulphite and 
Sulphate 


. Separation of Thiosulphates from 


Sulphides 


. Separation of Sulphides, Sul- 


phites, and Sulphates . 


. Separation of Silica from all other 


Acids 


. Detection of a Nitrite in ihe 


presence of a Nitrate 


. Detection of free Nitric Acid in 


the presence of a Nitrate 


. Detection of a Nitrate in the 


presence of an Iodide , 


. Separation of Chlorides, Bro- 
mides, and lIodides from - 
Nitrates 


. Separation of Cyanides "from 


Chlorides 


. Separation of Ferro- from Ferri- 


.Cyanides 


. Detection of Cyanides in the 


presence of Ferro- and Ferri- 
Cyanides 


. Detection of a Phosphate i in the 


presence of Calcium, Barium, 
Strontium, ie and 
Magnesium . 


. Detection of a Phosphate i in the 


presence of Iron 


. Separation of an Arseniate from 


a Phosphate . 


. Detection of a Fides in the 


presence of fixed Organic 
Acids which reduce Silver 
Salts 


. Separation of Oxalates, Tartrates, 


Citrates, and Malates 


. Detection of Carbolic Acid in the 


presence of Salicylic Acid 





TABLE OF CONTENTS. 


—eeSSSSSSSSSSSSSSSSSeEee 


CHAPTER IV. 


Qualitative Analysis, as applied to the Detection of Unknown Salts. 


ix 


. PAGE TABLES. 
§ I. General Preliminary Exami- PAGE 
nation . 58-60 | Full table for the Detection of the 
. Metal in a Simple Solution ; 62 
§ Il. Detection eee tl Table for the Detection of the Metal 
 teoureuinnny | Simple in a Simple Salt, limited to Salts 
Salt (with Tables for hotell P the Ph j 6 
same). : . 61-64 included in the Pharmacopeia 4 
Table for the detection of Metals in 
§ III. Detection of the Metals in mixtures of Pharmacopeceia Salts 
Complex Mixtures of two (facing) . J ; ; : ; 64 
or more Salts (with Tables Table for the Separation of Metals 
for same) . 65-74 into Groups . : i ; fet OG 
§ IV. Detection of the Acidulous tiie A, ake of Metals a 
: ge ofGroupI. . : ‘ . 
Beecats: : ‘ soe? Table B. cence of Metals 
Div, A. Preliminary Examina- of Group II., Div. (a). : 68 
tion . . 75 Table C. Separation of Metals 
» . Preparation ofSolution 77 of Group II., Div. (4). . 69 
; Table D. Separation of Metals 
» ©, Course for Inorganic of Group III., Div. (a) . ‘ 70 
Acids ag Table E. Separation of Metals 
» 0. Course for Organic of Group III., Div. (@), in pre- 
Acids : 80 sence of Phosphoric Acid ; 71 
1s Table F. Separation of Metals 
Solubility Tables 02, 63 ahGhoup Tt tie tase 42 
§ V. Special Processes for proving Table G. Separation of Metals 
/ the Identity of certain of.Group IV. . : : : 73 
readily recognisable Sub- Table H. Separation of Metals 
stances . 84-90 of Group V. : 4 74 
CHAPTER V. 
Qualitative Detection of Alkaloids, Glucosides, and certain Organic Bodies 
used in Medicine, with a General Sketch of Toxicological 
Procedure. 
Division A. Course for the Detection of the Alkaloids and’ Alkaloid Salts used in 
Medicine : : ; ; 5 , QI-93 
» . B. Qualitative Analysis of Scale Preparations : : ~ 93-95 
» C, Qualitative Detection of certain Glucosides, Resins, and Organic 
Bodies, other than Alkaloids ‘ A : : ; 95 
» ©. General Sketch of the Method of Testing for Poisons in Mixtures, 95-97 
»  £. General Resume’ of the Tests for all the chief Alkaloids (as under) . 97 
Aconitine, Colchicine. Narcéine. Sabadilline. 
Atropine. Colchiceine, Narcotine. Sabatrine. 
Beberine. Coniine. Nepaline. Solanine. 
Berberine. Curarine. Nicotine. Staphysagrine. 
Brucine. Delphinine. Papaverine. Strychnine. 
Caffeine. Delphinoidine, Physostigmine. Taxine. 
Calabarine. Emetine. Pilocarpine. Thalictrine. 
Chelidonine. Gelsemine. Piperine. Theobromine. 
Cinchonine. Hyoscyamine. Quinamine, Thebaine. 
Cinchonidine. Jervine. Quinidine. Veratrine. 
Codeine. Morphine. Quinine. Veratroidine. 


TABLE OF CONTENTS. 


PART I,—QUANTITATIVE ANALYSIS. 


CHAPTER VI. 
Weighing, Measuring, and Specific Gravity. 


PAGE 

1. Weighing and Measuring. 98-99 
2. Specific Gravity - . 100-106 
(a) Of Fluids . 100-102 
(5) Of Solids . 102-103 


CHAPTER VII. 
Volumetric Quantitative Analysis and Use of the “ Nitrometer.” 


I, Introductory Remarks 
A, Standard Solutions . 
B. Indicators ; 
C. General Modus Operandi . 
D. Apparatus employed 
E. Weighing operations : 
II. Standard Solution of Oxalic 
Acid § 
A, Preparation and Check 2 
B. Estimation of Alkaline 
Hydrates 
C, Estimation 
Carbonates : 
D. Estimation of Lead . 
E. Estimation of the Organic 
Salts of the Alkalies 
F. Official Standards 
Strength ‘ . 
III. Standard Sulphuric Acid . 
A. Preparation 
B. Uses. ; 
IV, Standard Solution of Sodium 
Hydrate : 
A. Preparation and Check 
B. Acidimetry ‘ 
C. Official Standards 
Strength 3 
D. Checking the Strength of 
Chloral Hydrate ‘ 
V. Standard Solution of Argentic 
Nitrate , , 
A. Preparation and Check 
B. Estimation of Soluble Ha- 
loid Salts 
C. Estimation of Hydrocyanic 
Acids. . ‘ 
D. Volhard’s Method 
£. Official Standards 
Strength : 
VI. Standard Solution of lodine 
A. Preparation and Check 
B. Estimation of Arsenious 


of *Riieihe 


of 


of 


of 


Acid. . 

C. Estimation of Sulphurous 
Acid 

D. Estimation of Thiosul- 
phates 


VII. Standard Solution ae Ssdiase 
Thiosulphate 


107 
107 
107 
108 
109 
109 


IIo 
IIo 


IIo 


Eat 
112 


112 


113 
114 
114 
114 


114 
114 
114 
115 
115 


115 
115 


115 


116 
116 


117 [ 


117 = 
117 


117 
117 
118 








118 | 


PAGE 
(c) Practical Applications of 

Specific olae 103 
(d@) OfGases . , 104 
(e) Vapor Density . 105-106 
A. Preparation and Check 118 
B. Estimation of Free Iodine 118 

C. Estimation of Free Chlorine 
and Bromine. 118 

D. Estimation of Available 
Chlorine Soy & 35 

E. Official Standards of 
Strength : 119 

VIII. Standard Solution of Potassium 
Bichromate . 119 
A. Preparation and Check 119 

B. Estimation of Ferrous 
Salts 3 : . £20 
C. Estimation. . of ~~ Ferric , 
Salts | ve 4 ‘ «. 22% 

D. Official Standards’ of 
Strength 2 121 

IX. Fehling’s Standard Solution of 
Copper i EET 
A. Manufacture and Check 121 
B. By Pavy’s Method 12 
C. Estimation of Sugar. 123 
D. Estimation of Starch 123 
X. Estimation of Phosphoric Acid . 123 

XI. Estimation of Sulphates by 
Standard Barium Chloride 124 

XII. Standard Mayer’s Solution for 
Estimation of Alkaloids 124 
XIII. Analysis by the Nitrometer 125 
A. General Remarks . « 125 

B. Estimation of Nitrous 
Ethero 125 

C. Estimation of Sodium Ni- 
trite ; 126 
D. Estimation of Ni itrates 126 

E. Estimation of Soluble Car- 
bonates . 126 

F. Estimation of Hydrogen 
Peroxide 127 
G. Estimation of Urea . 127 
XIV. Colorimetric Analysis 128 

A. Estimation of Ammonia by 
“‘Nesslerising ” 128 

B. Estimation of Nitrites in 
Water . 129 

C. Estimation of Minute Quan- 
tities of Copperor Iron, 129 

XV. Table of Coefficients for Volu- 
metric Analysis 130 


TABLE OF CONTENTS. x1 





CHAPTER VIII. 


Gravimetric Quantitative Analysis of Metals and Acids. 


PAGE PAGE 
Div. I. Preliminary Remarks . ~§. 131. 19. Estimation of Barium ., ey YAt 
A, Preparation of Filters. . 131 20. 3 ets CIN) eee TAL 
_ B. Estimation of Ashof Filters. 132 | 21. A » Magnesium <7 142 
C. Collection and Washing of ; 6 22, A , Potassium . oT 142 
Precipitates. ° 132 2%. i », sodium ? . t42 
D. Drying of Precipitates . ml 32 24. 7 » Potassium and 
E. Igniting and Ng of Sodium in presence of Metals 
Precipitates. 133 ofthe Fourth Group . ot 143 
F. Estimation of Moisture | . 134 25. Estimation of Ammonium 143 
G. es of Ashin Organic Div. III. Gravimetric Estimation of 
Bodies - Pn 1271 Acidulous Radicals . 144 
H. Use of Analytical Factors . 1 34 1. Chlorides . 3 : ~ 144 
Div. II. Gravimetric Estimation of Z.tlodides.- x: / : ‘ . 144 
the Metals. : oer 35 3. Bromides . : ‘ : . 144 
1. Estimation of Silver : 4. Cyanides . . 144 
A. As Chloride. , A « 185 5. Estimation of an Iodide in the 
B. As Metal. : S738 presence of a Chloride and 
2. Estimation of Lead : Bromide : : : «144 
A. As Oxide . : ‘ ee 6. Sulphides . : : : - ci44 
B. As Chromate : : 22it36 7. Sulphates . é ; : 2545 
3. Estimation of Mercury : 8. Nitrates . ; a pias 
A.’ As Metal. : : . 5136 A. In Alkaline Nitrates He TES 
B. As Sulphide. ‘ : : #136 B. As Nitric Oxide . : wants 
4- Estimation of Cadmium . <enl 37 C. As Ammonia ‘ eg eis 
rs of epee! 9. Estimation of Phosphates -aet4s 
A. As Oxide. : ~al37 A, Estimation of the strength 
B. As Metal. . e137 of Free Phosphoric Acid . 145 
6. Estimation of Bismuth : B, Alkaline Phosphates . at 4A6 
A. As Sulphide ‘ ; saets7 C. In presence of Calcium and 
B. As Oxide. ‘ : PP hicte) Magnesium ; 146 
7. Estimation of Gold . : «138 D. In presence of Iron and 
8. of Platinum . - e135 Aluminium : 146 
9. of Tin : E. Estimation as Phospho- 
A. As Oxide. ; , Sed iets) molybdate. ; 146 
B. As Metal. : , rakE38 10. Estimation of the “Total” and 
10. Estimation of Antimony . . 139 “Soluble” fate in a 
It, " of Arsenic: Manure or Soil. 146 
A. As Sulphide. ‘ ‘ 139 11, Estimation of Arseniates . : CUetAT 
B. As Magnesium - -Ammonium- 2. ij ,, Carbonates. </ea} 
Arseniate . : : we rsh 53. = », Oxalic Acid . 148 
12. Estimation of Cobalt : net 14. * » Lartaric Acid . 148 
13. & 5, Nickel F « 13140 15. »» dilicie Acid. IAG 
14. ss », Manganese. [149 A. Soluble Silicates . ; : lgs 
15. & _ eine’. . . 140 B. Insoluble Silicates ; 149 
16, < Pe AMOTip: . . 140 | Div. IV. Quantitative Separations : 
17. e » Aluminium. asp tae Full Mineral nals of 
18. . » Chromium . ae Water . : 149 
CHAPTER IX. 
Ultimate Organic Analysis. 
1. Apparatus required ' 152 (6) Process of Dumas : Rares e 4 
2. Estimation of Carbon and /‘By- (c) Kjeldahl’s Process : . 156 
drogen . : 153 | 4. Estimation of Chlorine . 157 
3. Estimation of Nitrogen . 155 | 5. Estimation of Bea oe and Phos- 
(a) Method of Varrentrapp and phorus. oe Ly | 


Will. = 155 


TABLE OF CONTENTS. 





xii 
CHAPTER X. 
Special Processes for the Analysis of Water, Air, and Food. 
PAGE PAGE 
Div, I. The Sanitary ae of 1. Estimation of Carbon Dioxide . 165 
Water : 158 2. Estimation of Organic Matter 165 
1. Collection of Sample 158 3. Testing for Gaseous Impurities. 165 
2. Color . : 158 ry. III. Food Analysis . 165 
3. Odor 158 . Milk . ; 165 
4. Suspended Solids 158 Table Degrees of Thermometer 167 
5. Total Solids 158 2. Butter , , 168 
6. Chlorine ‘ 159 3. Bread ; 169 
7. Nitrogen in Nitrates. 159 4. Alcohol (Estimation of) : . 169 
8. Nitrites 160 Table Percentages of Alcohol . 170 
g. Ammonia and Albuminoid Am- 5. Mustard 171 
monia 161 6, 7. Pepper and Coffee 171 
10. Oxygen Consumed 162 8. Colored Sweets 171 
11, Hardness . 163 g. Direct Estimation of Starch 
12. Judging the Results . , 164 (new process) 172 
Div. II. The Sanitary Analysis of Air 165 10. Vinegar 173 
CHAPTER XI. 
Special Processes for the Analysis of Drugs, Urine, and Urinary Calculi. 

Div. I. Analysis of Drugs 174 12, Estimation of Glycerine 184 

1, General Scheme of Dragen- Div. II. Analysis of Urine 184 
Corn =e 174 1. Specific Gravity 184 

2. Cinchona Bark . 176 2. Reaction 184 
A and B (American Method) 176 3. Deposit 185 

C (British Method) . : 177 4. Albumin (and estimation) 185 

32; Oprum was 179 5. Sugar (and estimation) 188 
4. Alkaloidal Strength of Extracts 179 6. Bile .. 189 
5. Methylated Spirit in Tinctures 180 7. Urea (and estimation) 190 
6. Strength of Resinous Drugs 181 8. Uric Acid be 190 
7. Testing the Purity of Quinine 9g. Phosphates ‘ 191 
Sulphate. 181 10. Sulphates . I9I 

8. Alkaloidal Strength of Scale 11. Chlorides . I9I 
' Preparations 182 12, Blood : 191 

g. Estimation of Phenol 182 | Div. III. Analysis of Urinary C Calculi 192 
10. Estimation of Fatty Acids in (a) Organic 192 
Soap : Labs (6) Inorganic . 192 

11. Estimation of Oleic Acid . 183 13. Form of Report 193 

CHAPTER XII. 
Analysis of Gases, Polarisation, and Spectrum Analysis. 

Div. I, Analysis of Gases by Keiser’s ADEM 194 
» lI. Analysis by the Polariscope . 197 
» III. Spectrum Analysis 5 199 
» IV. Melting Points 200 


Pre ol, 


QUALITATIVE ANALYSIS. 


| CHAPTER I. 
THE PROCESSES EMPLOVED BY PRACTICAL CHEMISTS. 


It is advisable that the student should understand the rvatson d’étre of the 
chief processes he will be called upon to employ, before commencing in detail 
the study of Analysis. 


I, SOLUTION. 


This process consists in stirring a solid body in contact with a fluid until 
it dissolves, heat being occasionally used. Bodies which refuse to dissolve 
in any particular fluid are said to be insoluble in it ; the liquid used is called 
the solvent, and sometimes the menstruum; a liquid having taken up all the 
solid matter possible is said to be saturated. A knowledge of the solubility 
of various substances in the chief menstrua, such as water, acids, alkalies, 
alcohol, ether, chloroform, and glycerine, is of the utmost importance. By 
this we are enabled to separate one body from another ; and by attention to 
minute details it is even possible to divorce bodies which are soluble in the 
same menstruum, but in different degrees. As an example we shall suppose 
three substances—one readily soluble, one partially so, and one but slightly 
soluble, in ether. By a careful use of three successive quantities of the 
liquid at different temperatures, we can obtain‘separate solutions of each. 
This process is named /ractional solution. In order to ascertain if any 
substance be soluble in any particular liquid, it is simply requisite to stir it 
into the fluid, applying heat if necessary. <A portion of the liquid is then 
poured off, and evaporated to dryness, when, if any of the solid was held 
in solution, it will remain as a visible residue. Asa general rule, the higher 
the temperature to which a liquid is raised, the greater becomes its capacity 
for saturation. Thus, one part of common nitre will require for solution 
about four parts of cold water ; but the same weight will dissolve in less than 
half a part of boiling water. There are many exceptions to this rule—notably 
that of calcium oxide, which is less soluble in boiling water than in cold: 
Many bodies, during solution, absorb so much heat that any substance placed 
in the liquid has its temperature remarkably reduced. Potassium nitrate and 
ammonium chloride, dissolved together in water, form in this manner a very 
efficient refrigerant when snow or ice is not obtainable. 


J 


2 CHEMICAL PROCESSES. 


reece anes ee ac ae SE SRR 


II. LIXIVIATION AND EXTRACTION. 


These processes include the digestion of a mixture of solids in a fluid, so 
as to dissolve the soluble portion. The solids, in the form of powder, are 
introduced into a vessel, and the water or other liquid having been added, 
the whole is well stirred. Remaining at rest until all the insoluble matter has 
subsided, the clear fluid, charged with all that was soluble in the mixture, 1s 
decanted, or poured off. On the large scale, in chemical works, the clear 
liquor is usually drawn off by means of a siphon. 

When a substance is to be extracted by means of a readily volatile solvent, 
such as ether or chloroform, the arrangement now commonly || 
used is that known as Soxhlet’s apparatus. This is illustrated 
in fig. 1. A flask (a) is charged with the solvent. The sub- 
stance (E) is put into a cartridge of filtering paper, and intro- 
duced into the Soxhlet tube (p); the latter is in turn connected 
with the upright condenser (c), through the jacket of which a 
stream of cold water is made to pass. Heat is now applied to 
the flask by a water-bath, and the vapour of the ether rising 
through B, condenses and drops on to the powder in the 
cartridge. When the instrument has become filled by the 
condensed solvent to the level of the top of F, it runs 
back into the flask charged with the soluble matter that has / 
been extracted. This process then repeats itself until the’ 
whole soluble portion has been extracted and transferred to 
the flask, which latter may then be attached to an ordinary 
condenser, and the solvent distilled off, leaving the soluble 
matters of the original powder in the flask. Resinous and 
sticky substances should be mixed with a little purified sand 
to prevent their clogging up the apparatus. 

Another method of extraction is that known as per- 
colation, a process much used in pharmacy. (| 
Ss a The apparatus employed is illustrated in 
xR fig. 2, The upper portion (A) is the per- 
colator, in which the powder to be extracted 
is tightly packed; and the solvent having 
been poured upon it, the whole is allowed to Fig. x. 
macerate for some time. The stopcock (c) being then opened, 
© the fluid gradually filters into the receiver (B), and more solvent is 
then poured on until the soluble portion of the contents of the 
percolator has been entirely transferred to the receiver. The con- 
necting tube is to prevent loss of volatile solvents. 


III, PRECIPITATION 


is the mixing of two substances in solution so as to form a third 
substance, which, being insoluble in the fluids employed, sinks to 
the bottom, and is called the precipitate. The clear liquid which 
a after the precipitate has settled down is called the supernatant 
iquid., 

When precipitates are totally insoluble in water, such as barium sulphate 
or argentic chloride, the operation is best conducted at a boiling heat, as 
the high temperature causes the precipitate to aggregate, so that it subsides 
rapidly, and is less liable to pass through the pores of the filter. 

On the other hand, there are some precipitates which must neyer be 
heated, but be allowed to form slowly by standing in the cold for several 
hours. To this class belong ammonium-magnesium phosphate, and potassium 
























Fig. 2. 


PRECIPITA TION—DECANTA TION—FILTRA TION. 3 





acid tartrate. When it is desirable to cause precipitates to form quickly, 
resort may be had to violent shaking, or stirring with a glass rod, so that it 
scrapes against the sides of the vessel. 

In qualitative analysis precipitation is usually conducted in test-tubes, 
shown in fig. 3. These are kept in a stand (fig. 4) having holes for the 
reception of tubes actually in use, and also a row of pegs upon which freshly- 





Fig. 6. 


washed tubes may be inverted to drain. Figure 5 illustrates the appliance 
used to hold tubes when their contents are to be boiled, and fig. 6 shows the 
brush used for cleansing them. 

In quantitative analysis precipitation is generally performed in beakers. 
These are very thin tumblers made of glass, free from lead, and annealed so 
as to permit their use with boiling liquids without risk of fracture. 

Precipitates are separated from the supernatant liquor by one of two 
methods. First :— 


IV. DECANTATION, 


which consists in allowing the precipitate to settle to 
the bottom, and pouring off the clear liquor. This is 
best done by the use of a glass rod held as shown in the 
illustration, fig. 7. Second:— 





V. FILTRATION, 


which consists in transferring the whole to a piece of folded filtering-paper 
or cloth placed in a funnel, so that the liquid passes through, while the 
precipitate remains. This may be washed by the addition of distilled water. 
The liquor which has thus passed’ through the filter is called the filtrate. 
The process of precipitation is probably one of the most common with which 
the practical chemist meets. . 
Specially prepared papers for filtration, cut into circles, are sold, and they 
have only to be folded to fit the funnel for which they are destined. The 





Fig. 8. Fig. 9. 


illustrations show, fig. 8 (A), the circle of paper, and (B) the same as folded 
for use, while fig. 9 represents the whole arrangement ready for use. 


4 CHEMICAL PROCESSES. 








VI. DISTILLATION 


is the changing of a fluid into vapor by the aid of heat, and passing the 
vapor into a cooling apparatus, called the condenser, where, its latent heat 
being abstracted, it is again deposited as a liquid. This process is employed 
for the separation of volatile fluids from non-volatile substances. The fluid 
which passes over and is condensed in the receiver is called the distillate ; 

7 while the non-volatile matter which remains 
in the retort is called the residue. Figure 1o 
shows the arrangement most commonly 
used in laboratories for small distillations. 
A is the retort in which the fluid is boiled, 
and B is called a Liebig’s condenser, through 
the jacket of which a stream of water is 
caused to pass, and beneath the end of this 
is placed a vessel (c) for the reception of 
the distillate. By careful attention to their 
boiling points, various volatile fluids may 
thus be separated from each other. Suppose, for example, that we have a 
mixture of three substances boiling respectively at 180°, 220°, and 240°, and 
their separation is desired, we should introduce the mixture into a retort fitted 
with a thermometer, the bulb of which was placed just above the level of the 
fluid. The whole being then attached to the condenser, the heat would be 
gradually raised until the thermometer marked a little over 180°, when that 
temperature would be steadily maintained as long as anything continued to 
collect in the receiver. When the liquid ceased to accumulate, the receiver 
would be changed, and the temperature raised to a little over 220°, and the 
distillation continued until the second liquid had ceased to pass over. The 
receiver being once more changed, the heat would be again raised, and 
maintained until the last liquid had been obtained as a distillate. This 


process, which is exceedingly useful in practical chemistry, is called fractional 
distillation. 





Fig. 10. 


VII. SUBLIMATION 


is the changing of a solid into a vapor by heat, and recondensing the vapor 
into a solid form in a cooled vessel. It is employed for the separation of 
volatile from non-volatile solids, and is thus conducted :—The substance to 
be sublimed is thinly spread over the bottom of a shallow iron pan, and the 
vessel is covered with a sheet of bibulous paper perforated with numerous 
pin-holes, or with a piece of muslin. By means of a sand bath, the heat is 
slowly raised to the desired degree, when the vapor passes through the 
strainer, and condenses in a cap of wood or porcelain, lined with stout 
cartridge paper, and placed over the heating-pan and kept cool. Fractional 
sublimation is often useful, and may be employed in a similar manner to 
fractional distillation. 


VIII. FUSION 


is the heating of a solid until it melts. It is usually carried out in a vessel 
called a “crucible,” made of fire-clay. On the small scale, or for the purposes 
of analysis, fusion is generally conducted in porcelain crucibles ; or, where the 
substances are such as would attack porcelain, in vessels of platinum or silver. 
Alkalies should be fused only in crucibles made of the latter metal. A 
peculiar kind of fusion, called cupellation, is resorted to in the assay of gold 
and silver. The alloy to be assayed is wrapped in a piece of lead foil, and 
the whole is then heated in a little cup made of bone ash, called a cupel, 
when the lead and all impurities fuse and sink into the substance of the 


EVAPORATION—CRYSTALLISATION AND DIALYSIS. § 





porous vessel, leaving the pure metal as a metallic button, which may then 
be weighed. The illustration (fig. 11) shows a set of crucibles for fusion—a, 
being of fire-clay ; B, a platinum crucible; c, one of porcelain ; and p, what 
is called Rose’s crucible, for heating substances in a current of hydrogen when 





it is desired to prevent access of air, or to produce rapid reduction to the 
metallic state. 
IX. EVAPORATION 


consists in heating a fluid until the whole, or as much of it as may be 
_ required, passes off in vapor. A solution thus treated until it has wholly 
passed into vapor is said to be evaporated to dryness, and the solid 
substance remaining is called the residue. 

Solutions containing any organic or volatile matter ought always to be 
evaporated on a water bath; that is, in a vessel exposed only to the heat of 
boiling water, in which the temperature must always be below 212° Fahr. 
(100° C.). With ordinary non-volatile or metallic substances in solution 
this precaution is unnecessary, and of no practical advantage. Evaporation 
may be conducted slowly, without raising the fluid to its boiling point, when 
it is called simple vaporisation; but when sufficient heat is applied, the 
evaporation takes place rapidly, and is accompanied by the disengagement of 
bubbles of vapor, and the fluid is then said to be in a state of ebullition. 
All liquids possess the continual desire, as it were, to pass into vapor ; and 
the amount of elastic force which the vapor thus given off exerts is called 
its tension. The more the liquid is heated, the greater becomes its tendency 
to vaporise, and consequently the more powerful is the tension of its vapor ; 
and when the latter is sufficiently marked to overcome the pressure exerted 
by the atmosphere and the cohesion of the liquid itself, ebullition takes place. 
The boiling point of a fluid is therefore the temperature at which the tenston of 
its vapor just exceeds that of the superincumbent atmosphere. If the pressure 
of the atmosphere be increased artificially, the boiling point of the liquid will 
rise in proportion. For example: boiling water in an open vessel under 
ordinary circumstances will have a temperature of 212°; but water in a steam 
boiler, under a pressure of 60 lb. per square inch, will be found to be heated 
nearly to 264°. As steam under pressure can thus be obtained at high 
temperatures, it is made use of for the rapid evaporation of liquids on a large 
scale, by causing it to pass into a jacket or through a coil of pipes surrounding 
the evaporating pan. The apparatus thus made use of is called a steam bath, 
the heat of which is usually understood to be about 2 30° Fahr. 

If water be boiled in a chemically clean glass vessel, and more particularly 
if a precipitate be suspended in the water, the boiling does not take place 
regularly, but the liquid becomes heated above its boiling point, and suddenly 
rushes into vapor in gusts. This is called by practical chemists ‘‘ bumping,” 
and may be prevented by putting in a few fragments of platinum foil, which 
act as nuclet, to aid in the regular disengagement of the vapor. 


X. CRYSTALLISATION AND DIALYSIS. 
Many substances when dissolved in a boiling liquid separate out, as soon 


6 CHEMICAL PROCESSES. 


as the fluid cools, in masses having a well-defined and symmetrical shape, 
bounded by plain surfaces and regular angles. These bodies are named 
crystalline; the deposited masses, crystals; and the remaining solution, the 
mother liquor. Substances which are not susceptible of crystallisation are 
called amorphous (z.e., formless) bodies ; while solids, such as glue and gums, 
which are soluble in water and yet not crystallisable, are named colloids. 
Crystallisation may also occur during solidification after fusion, and by the 
spontaneous evaporation of liquids holding crystalline substances in solution. 
All crystalline bodies invariably assume the same form, and may thus be 
unmistakably recognised from each other. The process is also useful for 
purification, as at the moment of crystallisation all impurities are rejected, 
and may be poured off with the mother liquor. Many circumstances affect 
the size of the crystals produced in any solution ; as a rule, the more rapidly 
crystallisation takes place, the smaller are the crystals. An example of the 
extreme variation in the size of the crystals produced from the same solution 
may be seen in ferrous sulphate. When allowed to deposit slowly, we have 
the ordinary well-marked commercial crystals ; but the same salt dissolved in 
boiling water, and the solution suddenly poured, with constant stirring, into 
spirit, gives granulated ferrous sulphate in crystals so minute that a lens is 
required to distinguish them. For the formation of large and well-defined 
crystals perfect rest is required, and it is often desirable to introduce pieces of 
wood or string so as to form nuclei on which the crystals collect. Good examples 
are seen in commercial crystallised sugar-of-milk and sugar-candy. Some bodies 
are capable of crystallising in two or more forms, and are called polymorphous. 
Instances of this property may be seen in mercuric iodide and in sulphur. 
When small quantities of crystalline substances exist in a solution together 
with a large quantity of uncrystallisable colloid bodies, their mutual separation 
is effected by dialysis. ‘This process consists in introducing the mixture into 
a glass vessel having a bottom made of vegetable parchment. This, called 
the dialyser, is floated in a large quantity of distilled water in a basin. At 
the expiration of several hours the whole of the crystalline bodies will have 
passed through the parchment, and will have become dis- 
solved in the water in the basin, while the colloids remain 
in the dialyser. A very good way of practising this process 
is to dialyse a solution of glue in which a few grains of salt 
have been dissolved, when the salt will be found to have 
passed into the water in the basin, while all the glue will © 
remain behind. This process is sometimes employed for 
the separation of crystalline poison, like strychnine, from the 
contents of astomach. ‘The rapidity of the dialysis is greatly 
Fig. 12. increased by causing a stream of water to pass through the 
outer basin, but of course this is only applicable where it is desired to retain 
the colloid body and not the crystalloid, as in the manufacture of the 
preparation known as dialysed tron. The apparatus used is shown in the 
illustration (fig. 12), in which a is the dialyser containing the mixture, while 
B contains the water into which the crystalline matter passes. 











fie | | l 


XI. ELECTROLYSIS. 


Electricity is one of the most powerful analytic forces with which the 
chemist has to deal. A current of electricity results from the action of 
chemical agents upon various metals, the apparatus in its simplest form being 
called a voltaic or galvanic cell or element, and a combination of several cells 
being termed a battery. Bunsen’s battery, which is very extensively used and 
of great power, consists of an outer cell or jar of glazed earthenware in which 


PYROLOGY. 7 


Serres 


is placed a cylinder of zinc, an inner unglazed porous jar and a rod of carbon, 
both furnished with binding-screws for attaching wires to them. ‘The acids 
used are dilute sulphuric around the zinc, and strong nitric in contact with the 
carbon in the inner cell. The zinc constitutes the positive (or most attacked), 
the carbon the negative (or least attacked) element; but when wires are 
attached to these, the end of the wire connected with the zinc is termed the 
negative electrode or cathode, whilst that in union with the platinum in the 
battery is the positive electrode or anode. ‘To explain this apparent contra- 
diction we must imagine that the current generated by the zinc passes through 
the fluid in the cell and then through the carbon, while at the same time an 
opposite current is generated from the carbon through the liquid to the zinc, 
and thus the effect of each current is felt at the ends of the wires from the 
opposite plate. These electrodes, when placed near one another in a com- 
pound liquid, occasion the phenomena of electrolysis, which is simply the 
splitting up of conductors of electricity into their elements or into simpler 
forms. For instance, a solution of HCI gives off Cl at the positive electrode 
and the H at the negative, as a result of the axiom that unlike electricities 
attract and like repel one another, Cl itself being electro-negative and H 
electro-positive. Dealing with H,SOu, we get H, at one electrode and SOx, at 
the other ; the latter, however, at once splitting up into O (given off) and SOs, 
which re-forms H,SO, with the water present. 

Further reference to applications of electrolysis will be found in Chapter X., 
when the student arrives at quantitative analysis. It is also applied in a 
modified form in qualitative analysis to the separation of tin and antimony. 


XII. PYROLOGY. 


Under this name are included all processes of analysis depending for their 
action on the use of fire, or, in other words, what were formerly called 
“yeactions in the dry way.” The chief instruments used are the blowpipe and 
the Bunsen burner. The blowpipe is a tube with a narrow nozzle, by which 
a continuous current of air can be passed into an ordinary flame. The ordi- 
nary gas flame consists of three parts: (2) A non-luminous nucleus in the 
centre; (4) A luminous cone surrounding this nucleus ; and (c) An outer 
and only slightly luminous cone surrounding the whole flame. The centre 
portion (a) contains unaltered gas, which cannot burn for want of oxygen, 
that necessary element being cut off by the outer zones. In the middle por- 
tion (4) the gas comes in contact with a certain amount of oxygen, but not 
enough to produce complete combustion; and therefore it is chiefly the 
hydrogen which burns here, the carbon separating and, by becoming intensely 
ignited, giving the light. In the outer zone (c) full combustion takes place, 
and the extreme of heat is arrived at, because chemical action is most intense. 
The outer flame therefore acts readily on oxidisable bodies, because of the 
high temperature and the unlimited supply of air, while the luminous zone 
tends to take away oxygen by reason of the excess of unburned carbon 
or hydrocarbons therein existing. For these reasons the former is called the 
oxidising flame, and the latter the reducing flame. The effect of blowing 
air across a flame is, first, to alter the shape of the flame, which is at once 
lengthened and narrowed; and, in the second place, to 
extend the sphere of combustion from the outer to the 
inner part (see fig.12@). As the latter circumstance causes 
an increase of the heat of the flame, and the former a 
concentration of that heat within narrower limits, it is easy 
to understand the great heat of the blow-pipe flame. The way of holding 
the blowpipe and the strength of the blast always depends upon whether the 


Fig, 12a, 


8 CHEMICAL PROCESSES. 





operator wants a reducing or an oxidising flame. The reducing flame is pro- 
duced by keeping the jet of the blowpipe just on the border of a tolerably 
strong gas flame, and driving a moderate blast across it. The resulting 
mixture of the air with the gas is only imperfect, and there remains between 
the inner bluish part of the flame and the outer barely visible part a luminous 
and reducing zone, of which the hottest point lies somewhat beyond the apex 
of the inner cone. To produce the oxzdising flame, the gas is lowered, the 
jet of the blowpipe pushed a little farther into the flame, and the strength of 
the current somewhat increased. This serves to effect an intimate mixture 
of the air and gas and an inner pointed, bluish cone, slightly luminous 
towards the apex, is formed, and surrounded by a thin, pointed, light-bluish, 
barely visible mantle. The hottest part of the flame is at the apex of the 
inner cone. Difficultly fusible bodies are exposed to this part to effect their 
fusion; but bodies to be oxidised are held a little beyond the apex, that 
there may be no want of air for their combustion. 

The current is produced by the cheek muscles alone, and not with the 
lungs. The way of doing this may be easily acquired by practising for some 
time to breathe quietly with puffed-up cheeks and with the blowpipe between 
the lips ; with practice and patience the student will soon be able to produce 
an even and uninterrupted current. 

The supports on which substances are exposed to the blowpipe flame are 
generally either wood charcoal, or platinum wire or foil. 

Charcoal supports are used principally in the reduction of metallic oxides, 
etc., or in trying the fusibility of bodies. The substances to be operated 
upon are put into small conical cavities scooped out with a 
penknife or with a little tin tube. Metals that are volatile at 
the heat of the reducing flame evaporate wholly or in part 
upon the reduction of their oxides; in passing through the 
outer flame the metallic fumes are re-oxidised, and the oxide 
formed is deposited around the portion of matter upon the 
support. Such deposits are called incrustations. Many of 
these exhibit characteristic colors leading to the detection 
of the metals. Thoroughly burnt and smooth pieces of charcoal only should 
be selected for supports in blowpipe experiments, as imperfectly burnt and 
knotty pieces are apt to spirt and throw off the matter placed on them. The 
method of employing a charcoal support is shown in fig. 12 J. 

The great use of charcoal lies (1) in its low degree of conductivity ; (2) its 
porosity, which causes it to absorb fusible bodies and leave infusible ones 
upon its surface; and (3) its power of aiding the effects of the reducing flame. 

Platinum wire and foil are used for supports in the oxidising flame, and 
the former is specially employed for trying the action of fluxes and the color 
communicable to the blowpipe or Bunsen flame. The platinum wire, when 
employed for making beads of borax or other fluxes, should be about 3 to 4 
inches long, with the end twisted into a small loop. The loop is then heated, 
and dipped while hot in the powdered borax, when it takes up a quantity, 
which is then heated till it fuses to a clear bead formed within the loop. 
When cold, this is moistened and dipped in the powder to be tested, and 
again exposed to the flame, and the effect noted. For trying the color 
impartable to the flame by certain metals, the wire is first cleaned by boiling 
in dilute nitric acid and then holding it in the flame until no color is obtained. 
The loop is then dipped in the solution to be tested, and held near the flame 
till the adhering drop has evaporated to dryness, and then heated in the 
mantle of the flame near the apex of the inner cone, and the effect observed. 

The Bunsen burner consists of a tube having at its base a series of holes 
to admit air, and also a small gas delivery tube. By means of this contrivance 





Fig, 12 5. 


PREPARATION OF SULPHURETTED HYDROGEN. 9 








the gas is mixed with air before it burns, and more perfect oxidation, and 
consequently much greater heat, is secured. Looking attentively at the flame 
of a Bunsen burner, we distinguish in it an inner part and two mantles sur- 
rounding it. The inner part corresponds to the dark nucleus of the common 
gas flame, and contains the mixture of gas and air issuing from the burner. 
The mantle immediately surrounding the inner part contains still some un- 
consumed carbide of hydrogen ; the outer mantle, which looks bluer and less 
luminous, consists of the last products of combustion. The Bunsen 
flame is illustrated in fig. 12¢. In it uo and Lo are respectively 
the upper and lower oxidising flames, and vu R and L R the upper 
and lower reducing ones. z F is the zone of fusion and is the hottest 
part, having a temperature (according to Bunsen) of 4,172° Fahr. The 
spot where the reducing action is the most powerful and energetic 
lies immediately above the apex of the inner part of the flame. The 
Bunsen flame brings out the coloration which many substances impart 
to flames, and by which the qualitative analyst can detect many 
bodies, even though present in such minute quantities that all other 









Ml means of analysis except the spectroscope fail to discover them. The 
Fig.12¢. subject of the coloration of flames will be discussed fully under 


each metal. 


XIII. PREPARATION OF SULPHURETTED HYDROGEN. 


This is done by acting upon ferrous sulphide with dilute sulphuric acid. 
The illustration (fig. 13) shows the apparatus. ‘The ferrous sulphide, broken 
into lumps the size of a nut, is placed in the generating bottle (a), and 
dilute sulphuric acid is poured in by the funnel (c) in small quantities as 
required. 8 is a bottle containing distilled water, through which the gas 





Fig. 15. 


passes to free it from any traces of acid mechanically carried over. Owing to 
the disagreeable odor, it is desirable to have special appliances, by means of 
which the evolution of the gas can be stopped as soon as it has done the work 
required. Such an apparatus for use in a large laboratory is that of Kipps 
(fig. 14); and one suitable for use by a single student is that of Van Babo 
(fig. 15). Both illustrations sufficiently explain themselves. 


CHAPTER adlds 
DETECTION OF THE METALS. 


For the purposes of qualitative analysis we employ certain chemicals, either 

in the solid or liquid state, which by producing given effects enable us to 

detect the existence of the substance searched for. These substances are 
always kept ready for use, and are called reagents. They are of three classes : 
ist, Group reagents, which, by yielding a precipitate under certain condi- 
tions, prove the substance to be a member of a certain group of bodies ; 
2nd, Separatory reagents, by means of which the substance under examination 
is distinguished from the other members of the group ; 3rd, Confirmatory 
reagents, by which the indications previously obtained are confirmed and 
renderéd certain. 

The Metals are divided into five groups, each of which has its group 
reagent, as follows :— 

Group 1. Metals the chlorides of which, being insoluble in water, are precipi- 
tated from their solution by the addition of hydrochloric acid. They 
are silver, mercurous mercury, and lead (the latter in cold strong 
solutions only). 

Group 2. Metals the sulphides of which, being insoluble in dilute hydro- 
chloric acid, are precipitated from their solutions by the addition of 
sulphuretted hydrogen in the presence of hydrochloric acid. This 
group includes mercury, lead, bismuth, copper, cadmium, antimony, 
tin, gold, platinum, and the metalloid arsenic, and is divided into two 
sub-groups, as follows :— 

A. Metals the sulphides of which are insoluble in both dilute 
hydrochloric acid and ammonium sulphide. The precipitated sul- 
phides separated by sulphuretted hydrogen are therefore insoluble, 
after washing, in ammonium sulphide. They are mercury, lead, 
bismuth, copper, and cadmium. 

&. Metals the sulphides of which, although insoluble in dilute acids, 
are dissolved by alkalies, and the precipitates from their solutions 
by sulphuretted hydrogen therefore dissolve in ammonium sulphide. 
They are gold, platinum, tin, antimony, and arsenic, 

Group 3. Embraces those metals the sulphides of which are soluble in dilute 
acids, but are insoluble in alkalies, and which consequently, having 
escaped precipitation in Group 2, are now in turn precipitated by 
ammonium sulphide. They are iron, nickel, cobalt, manganese, and 
zinc. In this group are likewise included aluminium, cerium, and 
chromium, which are precipitated as hydrates by the alkalinity of the 
ammonium sulphide. Magnesium would also be precipitated as 
hydrate, but, as that would be inconvenient at this stage, its precipi- 
tation is prevented by the addition of ammonium chloride, in which 
its hydrate is soluble. 


SIZ VER. I! 


eee FSS 


Group 4. Comprises metals the chlorides and sulphides of which, being 
soluble, escape precipitation in the former groups, but the carbonates 
of which, being insoluble in water, are now precipitated by ammonium 
carbonate. They are barium, strontium, and calcium. Magnesium 
is not precipitated as carbonate, owing to the presence of the ammonium 
chloride already added with the sulphide in Group 3. 

Group s. Includes metals the chlorides, sulphides, and carbonates of which, 
being soluble in water or in ammonium chloride, are not precipitated 
by any of the reagents already mentioned. They consist of magne- 
sium, lithium, potassium, sodium, and ammonium. 

As the analytical grouping of the metals is undoubtedly one which is most 
important to the student for practical purposes, we shall adhere to this 
arrangement in giving the methods for their detection. 


GROUP I. 


Metals precipitable as chlorides by the addition of hydrochloric acid toy. 
their solutions. Ay 


J 2 
I. SILVER (Ag). Pe W 
(2) WET REACTIONS. | TY" 


(To be practised upon a solution of argentic nitrate—AgNO,,) 


1. Hydrogen chloride (Aydrochloric acid)—HO@l (1st group reagent)—or any 
soluble chloride gives a curdy white precipitate of argentic chloride— 
AgCl—insoluble in boiling nitric acid, but instantly soluble in ammo- 
nium hydrate. It is also soluble in KCy, Na,S,O3, and in strong 
solutions of soluble chlorides. 

2. Potassium hydrate—KHO—or sodium hydrate—NaHO—both produce 
a brownish precipitate of argentic oxide—Ag,O— insoluble in excess. 
A similar effect is produced by the hydrates of barium, strontium, and 
calcium. 

3. Potassium chromate—K,Cr0,—gives a red precipitate of argentic chromate 
—Ag,CrO,—soluble in large excess of both nitric acid and ammonium 
hydrate; and therefore the solution should always be as neutral as 
possible. 

4. Hydrogen sulphide—H,S—and ammonium hydrogen sulphide—NH,HS— 
both produce black argentic sulphide—Ag,S—insoluble in excess, 
both soluble in strong boiling nitric acid. 

5. Potassium iodide—KI—and potassium bromide—KBr—both produce 
curdy precipitates, the former yellow argentic iodide—AgI—insoluble in 
ammonium hydrate, and the latter argentic bromide—AgBr—dirty-white 
and slowly soluble in ammonium hydrate. 

6. Potassium cyanide—KCy—gives a curdy-white precipitate of argentic 
cyanide—AgCy—readily soluble in excess, and also in boiling strong 
nitric acid. 

7. Many organic salts, such as formates and tartrates, boiled with solutions of 
silver, precipitate the metal as a mirror on the tube. 

8. Fragments of copper, zinc, iron, and tin, introduced into a solution of 
silver, all precipitate the metal. : 


(6) DRY REACTION. 


(To be practised on argentic oxide—Ag,O.) 


Mixed with sodium carbonate and heated on charcoal before the blowpipe, 
a bead of silver is formed, hard, glistening, and soluble in nitric acid, yielding 
solution of argentic nitrate to which the wet tests may be applied. 


12 DETECTION OF THE METALS. 


II. MERCUROSUM (Hg,)’ ee 
(2) WET REACTIONS. 
(To be practised on a solution of mercurous nitrate—(Hg,)” (NO3),—prepared 
by acting upon a globule of mercury with cold and dilute nitric acid.) 


1. HCl (1st group reagent) gives a white precipitate of mercurous chloride, 
— (Hgs)"Cl,’ — turned to black mercuros-ammonium chloride — 
NH,(Hg,)"Cl'—by ammonium hydrate. It is also insoluble in boiling 
water, but soluble in strong nitric acid, being converted into a mixture 
of mercuric chloride—HgCl,—and mercuric nitrate—Hg(NO,).. 

2. KHO and NaHO both give black precipitates of mercurous oxide—Hg,O— 
insoluble in excess. 

3- Ammonium hydrate—NH,HO—produces a black precipitate of dimercuros- 
ammonium nitrate—NH,(Hg.)” NO,;H,O—also insoluble in excess. 

4. Stannous chloride—SnCl,—boiled with the solution causes a grey precipitate 
of finely divided mercury, which, if allowed to settle, and then boiled 
with hydrochloric acid and some more stannous chloride, aggregates 
into a globule. 

5. KI gives a green precipitate of mercurous iodide—Hgl. 


(4) DRY REACTION. 
(To be tried upon mercurous iodide.) } 


Mercurous compounds heated, break up into the corresponding mercuric 
salt and metallic mercury, and finally sublime. 


III. LEAD (Pb). Sis 
(2) WET REACTIONS. ses 
(To be practised on a solution of plumbic acetate—Pb(C,H30,),.) 


1. HCl (15¢ croup veagent) forms in cold strong solutions a white precipitate 

of plumbic chloride—PbCl,—soluble in boiling water. 

2. HS after acidulation by HCl (2nd group reagent) gives a black precipitate 
of plumbic sulphide—PbS—insoluble in ammonium sulphide. By 
treatment with boiling strong nitric acid it is decomposed, partly into 
plumbic nitrate, but chiefly into insoluble plumbic sulphate. It is 
entirely dissolved by hot dilute nitric acid with separation of sulphur. 

3. Hydrogen sulphate (su/phuric acid) —H,80,—gives a white -precipitate of 
plumbic sulphate—PbSO,—slightly soluble in water, but rendered 
entirely insoluble by the addition of a little alcohol It is decomposed 
by boiling strong hydrochloric acid, and is also freely soluble in 
solutions of ammonium acetate or tartrate, containing an excess of 
ammonium hydrate. 

4. K,Cr0, gives a yellow precipitate of plumbic chromate—PbCrO,—insoluble 
in acetic and yery dilute nitric acids, but soluble in strong boiling 
nitric acid. 

5. KI gives a yellow precipitate of plumbic iodide—PbI,—soluble in 33 parts 
of boiling water, and crystallising out on cooling in golden scales. 

6. KHO and NaHO both cause white precipitates of plumbic hydrate— 
Pb(HO),—soluble in excess, forming potassium or sodium plumbates 
—K,PbOz and Na,PbO,. 

7. NH,HO causes a white precipitate of a white basic nitrate—Pb(N 0;HO)— 
insoluble in excess. 

8. KCy produces a white precipitate of plumbic cyanide—PbCy,—insoluble 
in excess, but soluble in dilute nitric acid. 





MERCURICUM. 13 


ED 


9. Alkaline Carbonates cause a precipitate of (PbCO3),Pb(HO),—“ White 
lead »—insaluble in excess, and also in potassium cyanide. 
10. Fragments of zinc or iron in the presence of afiittle acetic acid cause the 
separation of metallic lead in crystalline lamine. 


(4) DRY REACTION. 
(To be practised on red lead—Pb;O,, or litharge—PbO.) 


Heated on charcoal in the inner blowpipe flame, a bead of metallic lead is 
formed, which is soft and malleable, and soluble in dilute nitric acid. The 
solution thus obtained gives the wet tests for lead. 


GROUP II. ° 


Metals which are not affected by acidulation with hydrochloric acid, but are 
precipitated by passing sulphuretted hydrogen through the acidulated solution. 


DIVISION A. 


Metals. which, when precipitated by sulphuretted hydrogen as above, yield 


sulphides insoluble in ammonium sulphide. rs 


I. MERCURICUM (Hg).’ 


(a) WET REACTIONS. 
(To be practised on a solution of mercuric chloride—HgCl,.) 


1. H,S after acidulation by HOl (2nd group reagent) gives a black pre- 
cipitate of mercuric sulphide—HgS— insoluble in ammonium sulphide 
and nitric acid, and only soluble in nitro-hydrochloric acid. Care 
must be taken that the sulphuretted hydrogen is passed really in excess, 
and that the whole is warmed gently, as unless this be done, the pre- 
cipitate is not the true sulphide, but a yellowish-brown dimercuric 
sulpho-dichloride—Hg,SCl,. Although insoluble in any single acid, 
mercuric sulphide may be caused to dissolve in hydrochloric acid by 
the addition of a crystal of potassium chlorate. 

2. KHO or NaHO both give a yellow precipitate of mercuric oxide—HgO— 
insoluble in excess. 

3. NH,HO produces a white precipitate of an insoluble mercur-ammonium 
chloride—(NH,Hg)Cl—also insoluble in excess. 

4. KI yields a red precipitate of mercuric iodide, soluble in excess both of 
the precipitant and the mercuric salt. 

s. SnCl,, boiled with a mercuric solution, first precipitates mercurous chloride, 
and then forms metallic mercury, as in the case of mercurosum 
compounds. 

6. Alkaline Carbonates (except ammonium carbonate) produce an immediate 
reddish-brown precipitate of mercuric oxy-carbonate. 

. Fragments of Cu, Zn, or Fe precipitate metallic mercury in the presence 
of dilute hydrochloric acid. 


(3) DRY REACTION. 


(To be tried on mercuric oxide—HgO—and on “ Ethiops mineral ”—HgS.) 


All compounds of mercury are volatile by heat ; the oxide breaking up into 
oxygen and mercury, which sublimes, while the sulphide sublimes unaltered 
unless previously mixed with sodium carbonate or some reducing agent. 





sd © 
14 _ DETECTION OF THE METALS. 


° II. BISMUTH (Bi). , 

ry WET REACTIONS. ®° | 

(To be practised upon bismuth subnitrate, dissolved in water by the aid of 

; the smallest possible quantity of nitric acid, and any excess of the latter 

@ . carefully boiled off. This solution will, then contain bismuth nitrate— 
Bi(NOs)z. 

. HS after acidulation by HCl (2nd group veagent) gives a black precipitate 
of bismuth sulphide—Bi,S,—insoluble in ammonium sulphide, but 
soluble in boiling nitric acid. : 

. H,S0, gives no precipitate (distinction from lead). | 

. NH,HO, KHO, and NaHO, all give precipitates of white bismuthous hydrate 
—bi,H,O% or BiO(HO),—insoluble in excess, and becoming converted 
into the yellow oxide—Bi,O,—on boiling. 

. Water—H,0— in excess to a solution in which the free acid has been as 
much as possible driven off by boiling, gives a white precipitate of a 
basic salt of bismuth. ‘This reaction is more delicate in the presence 
of hydrochloric than of nitric acid ; and the precipitate, which is in this 
case bismuth oxy-chloride—BiOCI—is insoluble in tartaric acid (dis- 
tinction from antimonious oxy-chloride). 

. K,Cr0, yields a yellow precipitate of bismuth oxy-chromate—Bi,0,CrO,— 

; e soluble in dilute nitric acid, but not in potassium hydrate (distinction 

from plumbic chromate). 

6. KI gives brown bismuthous iodide, soluble in excess. 





I 





Ot 


7. Alkaline Carbonates give white precipitates of bismuth oxy-carbonate, 
insoluble in excess. : 
8. Fragments of zine added to a solution of bismuth cause a deposit of the 


metal as a dark grey powder. . 


(6) DRY REACTION. 
(To be practised upon dismuth subnitrate.) 


Mixed with sodium carbonate—N a,CO3;—and heated on charcoal before the 
blowpipe, a hard bead of metallic bismuth is produced, and the surrounding 
charcoal is incrusted with a coating of oxide, deep orange-yellow while hot 
and pale yellow on cooling, 


III. COPPER (Cu.) SB f 
(a) WET REACTIONS. pe 
(To be practised with a solution of cupric sulphate—CuSO,.) 


1. HS after acidulation with HCl (2nd group reagent) forms a precipitate of 
brownish-black cupric sulphide—CuS—which is nearly insoluble in 
ammonium sulphide, but soluble in nitric acid. Its precipitation is 
prevented by the presence of potassium cyanide (distinction from 
cadmium). When long exposed to the air in a moist state, it oxidises 
to cupric sulphate and dissolves spontaneously. 

. NH,HO causes a pale blue precipitate instantly soluble in excess, forming a 
deep blue solution of tetrammonio-cupric sulphate—(N H;),CuSO,H,0. 

3. Potassium ferrocyanide—K,FeCy,—yields a chocolate-brown precipitate of 

cupric ferrocyanide—Cu,FeCy,. This test is very delicate, and is not 
affected by the presence of a dilute acid, but does not take place in an 
alkaline liquid. ; 

4. KHO or NaHO precipitates light-blue cupric hydrate—Cu(HO),—insoluble 


N 


in excess, but turning to black cupric oxy-hydrate—(CuO),Cu(HO),— sake 


on boiling. 


CADMIUM—ARSENIC. 15 
DE 2 aS EELS SC EO 
5. Potassium sodium tartrate (Rochelle salt)—KNaC,H,0,—and NaHO added 
successively, the latter in excess, produce a deep blue liquid (Fehling’s 
solution), which when boiled with a solution of glucose (grape sugar) 
deposits brick-red cuprous oxide—Cu,0. ai 
6. The Alkaline Carbonates behave like their respective hydrates. 


4, Fragments of zinc or iron precipitate metallic copper from solutions acidu- 
Y . lated with HCl. | 
(6) DRY REACTIONS. 

(To be practised upon cupric oxide—CuO—or verdigris—Cu, O(C,H302)2-) 
1. Heated with NasCO3 and KCy on charcoal, in the inner blowpipe flame, , 

red scales of copper are formed. | 
_ Heated in the borax bead before the outer blowpipe flame, colors it gree 
while hot and blue on cooling. By carefully moistening the bead wit 
SnCl, and again heating, this time in the inner flame, a red color is 
produced. , 












tN 


IV. CADMIUM (Cd). 
(a) WET REACTIONS. 
(To be practised with a solution of cadmium iodide—CadlI,.) 


1. HS after acidulation with HCl (2nd group reagent) gives a yellow precipi- 
tate of cadmium sulphide—CdS—insoluble in ammonium sulphide, / 
but soluble in boiling nitric acid. This precipitate does not form 
readily in presence of much acid ; but its production is not hindered 
by the addition of potassium cyanide (distinction from copper). 

2. NH,HO produces a white precipitate of cadmium hydrate—Cd(HO)2— 
soluble in excess. 

_ KHO or NaHO both give precipitates of cadmium hydrate—Cd(HO).— 

insoluble in excess (distinction from zinc). 

4. Alkaline Carbonates precipitate cadmium carbonate—CdCO,—insoluble 
in excess. 


oo 


(6) DRY REACTION. 
(To be practised on cadmium carbonate—CdCQ3.) 


Heated on charcoal before the blowpipe, a brownish incrustation of oxide 
is produced, owing to reduction of the metal and its subsequent volatilisation 
and oxidation by the outer flame. 


DIVISION B. : 


Metals which are precipitated by sulphuretted hydrogen in the presences of 
hydrochloric acid, but yield sulphides which are soluble in ammonium sulphide. 


I, ARSENIC (As). ~~ 
(2) WET REACTIONS. | 


_ (To be practised with a solution of arsenious anhydride in boiling water 
slightly acidulated by hydrochloric acid.) 


1. HS, after acidudation with HCl, causes a yellow precipitate. of arsenious. 
sulphide—As,S;—soluble in ammonium sulphide, forming ammonium 
sulpharsenite—(N H4)3AsS,;—but insoluble in strong boiling hydro- 
chloric acid (distinction from the sulphides of Sb and Sn). This 
precipitate is also soluble in cold solution of commercial carbonate of 
ammonia (distinction from the sulphides of Sb, Sn, Au, and Pt). Dried . 


16 DETECTION OF THE METALS. 





and heated in a small tube with’ a mixture of NagCO; and KCy, it 
yields a mirror of arsenic. (Detects 1 part of As in 8,000.) 

2. Boiled with KHO and a fragment of Zine, arseniuretted hydrogen—AsH,— 
is evolved, which stains black a paper moistened with solution of 
argentic nitrate and held over the mouth of the tube during the ebul- 
lition (#Zectmann’s test). 

3- Boiled with 7 of its bulk of HCl and a slip of Copper, a grey coating is” 
deposited on the copper of cupric arsenide. On drying the copper 

_ carefully, cutting it into fragments, and heating in a wide tube, a 
: crystalline sublimate of arsenious anhydride—As,O,— 
is obtained, which, when examined by a lens, is seen to 
be in octohedral crystals, and, when dissolved in water, 
gives a yellow precipitate of argentic arsenite—Ag,AsO, 
—with solution of ammonio-nitrate of silver (Reduch’s 
test). (Detects 1 part As in 40,000). : 

4. Placed in a gas bottle furnished with a jet (illustrated in 
the margin), together with dilute sulphuric or hydro- 
chloric acid and a few fragments of zinc, arseniuretted 
hydrogen—AsH;—is evolved, which may be lighted 
at the jet, and burns with a lambent flame, producing 

As,O3. If a piece of cold porcelain be held in the flame, dark spots of 

arsenic are obtained, readily volatile by heat and soluble in solution 

of chlorinated lime (Zarsh’s test). (Detects 1 part As in 200,000,000.) 


/Vote.—For reactions of arsenites and arseniates, see Acidulous Radicals. 








(6) DRY REACTION. 
(To be practised on arsenious anhydride—As,QO3.) 


Heated in a small tube with Na,CO; and KCy, a mirror of arsenic is pro- 
duced, accompanied by a garlic-like odour. The same effect may be produced 
with black flux. ; 


II, ANTIMONY (Sb). 
(a) WET REACTIONS. 
(To be practised with a solution of tartar emetic (K(SbO)C,H40,).H,O.) 


1. HS, after acidulation by HCl, causes an orange precipitate of antimonious 
sulphide—Sb,S,—soluble in ammonium sulphide, forming ammonium 
sulphantimonite—(NH,),SbS;—also soluble in strong boiling hydro- 
chloric acid, forming antimonious chloride—SbCl,—but insoluble in 
cold solution of commercial carbonate of ammonia. 

2., KHO and NaHO produce precipitates of antimonious oxide readily soluble 
in excess to form antimonites (K3SbO, or NagSbO;). 

3. Acidulated with HCl and introduced into a platinum dish with a rod of 
zine so held that it touches the platinum ow¢szde the liquid, a black 
stain of metallic antimony is produced closely adherent to the platinum. 
This stain is not dissolved by HCl (tin reduced in the same manner 
is granular and soluble in boiling HC\). 

4: Reinch’s test (see Arsenic) produces a black coating on the copper, which, 
when heated, forms an amorphous sublimate of Sb2O, close to the copper, 
and insoluble in water, but dissolved by a solution of cream of tartar 
in which H.S then produces the characteristic orange sulphide. 

5. Marsh’s test (see Arsenic) yields stains of antimony on the porcelain, not 
nearly so readily volatile by heat as in the case of arsenic, and not 
discharged by solution of chlorinated lime. 


TIN—GOLD. . 17 





6. Fleitmann’s test will not act with antimony at all (distinction from 
arsenic). 


(4) DRY REACTION. 
(To be practised on antimonious oxide—Sb,O3.) 


Heated on charcoal with Na,CO, and KCy before the blowpipe, a bead 
of metallic antimony is formed and copious white fumes of the oxide are 
produced. 





III. TIN (Sn' or Sn’), md 
(a) WET REACTIONS. ' 


(To be practised with a solution of stannous chloride—SnCl,—and one of | 
stannic chloride—SnCl,—prepared by warming the stannous solution with — 
a little nitric acid.) 





- 


. HS, after acidulation with HCl, produces a brown or yellow precipitate 

) of SnS or SnS, respectively, both soluble in ammonium sulphide and 
in boiling hydrochloric acid. 

_ KHO or NaHO both produce white precipitates of Sn(HO), or Sn(HO)a, 
soluble in excess, the former to produce stanmnites and the latter stan- 
nates. The stannous solution is, however, reprecipitable on boiling, 
while the stannic is not. 

. NH,HO produces similar precipitates, very difficultly soluble in excess. 

. Acidulated by HCl, and introduced into a platinum dish with a rod of 
zine, so held in the fluid that it touches the platinum owés¢de the liquid, 
granules of metallic tin are deposited, soluble in boiling HCl, to form 
stannous chloride. 

s, HgCl, boiled with stannous salts deposits a grey precipitate of metallic 

mercury. 


NS 


Rw 


(3) DRY REACTION. 


(To be practised on putty owder—SnO,,.) 


Heated on charcoal with Na,COs before the blowpipe, a bead of metallic 
tin is produced, and a white incrustation of oxide is formed on the charcoal. 


IV. GOLD (Au). SG 
(a) WET REACTIONS. . 
(To be practised with a solution of auric chloride—AuC],.) 


1. HS (group reagent) in the presence of HCl gives black auric sulphide 
—Au,§$3. If the solution be hot, aurous sulphide—Au,S—falls. Both 
are only soluble in nitro-hydrochloric acid, but they are soluble in 
ammonium sulphide when it is yellow. 

. NH,HO precipitates reddish ammonium aurate, or fudminating gold— 
Au,(NH;),.0,—but KHO gives no result. 

3. Hydrogen oxalate (oxalic acid)—H,C,0, (or Ferrous sulphate—FeS0,) 
—when boiled with an acid solution throws down Au. Reducing agents 
generally act thus. The liquid containing the metal may exhibit a blue, 
green, purple, or brown color. 

. $nCl, throws down a brownish or purplish precipitate, known as “ purple 
of Cassius,” consisting of the mixed oxides of gold and tin. 

_ Zn, Cu, Fe, Pt, or almost any metal, gives a precipitate of metallic Au in 
a finely divided state. 


NS 


as 


on 


2 





18 DETECTION OF THE METALS. 


(4) DRY REACTION. 
(To be practised on any gold salt.) 
Heated on charcoal with Na,COs;, the metal is produced. 


V. PLATINUM (Pt). 
(2) WET REACTIONS. . 
(To be tested with a solution of platinic chloride—PtCl,.) — 


1. HS (2d group reagent) in presence of HCl gives a drown precipitate of 
platinic sulphide—PtS2. This precipitate forms slowly, and is readily 
dissolved by yellow ammonium sulphide. 

2. Potassium chloride—KCl—ix presence of HCl, especially after addition of 
alcohol, produces a yellow crystalline precipitate of potassium platinic 
chloride—PtK,Cl,—soluble to a moderate extent in water, but not in 
alcohol. Decomposition takes place when this is strongly heated, 
metallic Pt and KCl remaining. 

3. Ammonium chloride—NH,Cl—gives a precipitate of ammonium platinic 
chloride—Pt(NH,),Cl,—which is almost identical in properties, but 
is more readily decomposed by heat, pure platinum remaining. 

4. 2n, Fe, and several other metals decompose platinic salts with the produc- 
tion of the metal. 


(6) DRY REACTION. 
(To be practised upon potassium platinic chloride—PtK,Ck.) 


Heat on charcoal, with or without Na,CO3, before the blowpipe. The 
metal is produced by reduction. 


GROUP III. 


Metals which escape precipitation by sulphuretted hydrogen in presence 
of hydrochloric acid, but which are precipitated by ammonium sulphide in the 
presence of ammonium hydrate, ammonium chloride having been previously 
added to prevent the precipitation of magnesium. 


DIVISION A. 


Metals which, zz the insured absence of organic matter, are precipitated as 
hydrates by the addition of the ammonium chloride and ammonium hydrate 


only. 
I. IRON (Ferrous, Fe; and ferric, Fe,). @ 
(2) WET REACTIONS. 


(To be practised successively on solutions of ferrous sulphate—FeSO,—and 
ferric chloride—Fe2C],. ) 


1. NH,HO 7x the presence of NH,Cl (group reagent) yields either a dirty- 
green precipitate of ferrous hydrate—Fe(HO),—or a reddish-brown 
precipitate of ferric hydrate—Fe,(HO),. ‘The former is sdzght/y soluble 
in excess, but the latter is insoluble, and it is therefore preferable 
always to warm the solution with a little nitric acid, to insure the 
raising of the iron to the ferric state, before adding the ammonium 
hydrate. The presence of organic acids, such as tartaric or citric, 





IRON. 19 


prevents the occurrence of this reaction; and therefore, if any such 
admixture be suspected, the solution should first be evaporated to dry- 
ness, the residue heated to redness, and then dissolved in a little 
hydrochloric acid, heated with a drop or two of nitric acid, diluted, 
and lastly, the NH,Cl and NH,HO added and boiled. 

. NH,HS, added to a neutral or alkaline solution, produces a precipitate 
of ferrous sulphide—FeS—which is black (distinction from Al, Ce, 
Cr, Mn, and Zn), and readily soluble in cold diluted hydrochloric 
acid (distinction from the black sulphides of Ni and Co). This. re- 
action takes place even in the presence of organic matter, and the 
precipitated sulphide, if exposed to the air, gradually oxidises to fer- 
rous sulphate—FeSO,—and disappears. It is insoluble in acetic acid 
(distinction from MnS). 

. K,FeCy,, in a neutral or slightly acid solution, gives, with ferrous salts, a 
white precipitate (rapidly changing to pale blue) of Everett’s salt—potas- 
sium ferrous ferrocyanide—KeFe * FeCy,—and with ferric salts, a dark 
blue precipitate of Prussian blue—ferric ferrocyanide (Fe,)(FeCyg)3. 
These precipitates are decomposed by alkalies, producing the hydrates 
of iron, and forming a ferrocyanide of the alkali in solution; but the 
addition of hydrochloric acid causes the re-formation of the original 
precipitate. 

. Potassium ferricyanide—K,Fe.Cy,.—gives, with ferrous salts, in neutral or 
slightly acid solutions, a dark blue precipitate of Turnbull’s blue— 
ferrous ferricyanide, Fe,Fe,Cy,.—but with ferric salts it gives no pre- 
cipitate, simply producing a brownish liquid. With alkalies, Turnbull’s 
blue is decomposed, yielding black ferroso-ferric hydrate, and a ferri- 
cyanide of the alkali; but the addition of hydrochloric acid reproduces 
the original blue. 

. Potassium thiocyanate (su/phocyanate)—KCyS—gives no precipitate with 
ferrous salts, but with ferric compounds it yields a deep blood-red 
solution. This colour is not discharged by dilute hydrochloric acid 
(distinction from ferric acetate), but immediately bleached by solution 
of mercuric chloride (distinction from ferric meconate). 

. KHO, or NaHO, produces effects similar to those of ammonium hydrate. 

. Disodium phosphate—Na,HP0O,—7x the presence of NaC,H;0, ov NH,C,H,0, 
—gives a whitish gelatinous precipitate of ferrous or ferric phosphates— 
Fe,(PO,),. or Fe,(PO,)2—insoluble in acetic acid, but soluble in hydro- 
chloric acid. The previous addition of citric or tartaric acids prevents 
this reaction. 

. Sodium acetate—NaC,H.0,—added in excess to ferric salts, produces a deep 
red solution of ferric acetate—Fe,(C,H;0,),—which on boiling deposits 
as a reddish-brown ferric oxyacetate—Fe,O(C,H30,)4. This precipi- 
tate dissolves slightly on cooling; but iron can be entirely precipitated 
in this form if the solution be instantly filtered while hot. 

. Alkaline Carbonates, added to a ferrous salt, precipitate white ferrous 
carbonate—FeCO,—but with ferric salts throw down the reddish-brown 
ferric hydrate already described. 


(3) DRY REACTIONS. 
(To be practised on ferric oxide.) 


. Heated on charcoal before the inner blowpipe flame, a black magnetic 
powder is obtained, which is not the metal, but is ferroso-ferric oxide 
—Fe,0,. 

. Heated in the borax bead in the inner blowpipe flame, a bottle-green 





ah 


20 DETECTION OF THE METALS, 


color is produced ; but in the outer flame the bead is deep red while 
hot, and very pale yellow when cold. 


II. CERIUM (Ce). 


(a) WET REACTIONS. 


(To be practised on cerous chloride—CeCl,—prepared by boiling cerium 
oxalate with sodium hydrate, washing the insoluble cerous hydrate with 
boiling water, and dissolving it in the least possible excess of hydrochloric 
acid.) 


1. NH,HO zx the presence of NH,Cl (group reagent) gives a white precipitate 
of cerous hydrate—Ce(HO),—insoluble i in excess. 

2. KHO and NaHO give a similar precipitate, turning to yellow ceroso-ceric 
oxide—Ce,0,—on the addition of chlorine water. 

3. Ammonium oxalate—(N H,).0,0,—gives a white precipitate of cerous oxalate 
—CeC,O,—insoluble in excess, and not readily dissolved even by hydro- 
chloric acid. The presence of citric or tartaric acid does not interfere 
with this reaction. | 

4. Potassium sulphate—K,S0,-—in a saturated solution causes the formation 
of white crystalline potassium cerium sulphate Ce(SOx4).—soluble 
in hot water. 


(6) DRY REACTIONS. 


(To be practised on cerium oxalate.) 


- Heated to redness in contact with the air, a deep red residue of ceric 
oxide—Ce,O3—is obtained, difficultly soluble even in strong hydro- 
chloric acid. 

2. Heated in the borax bead, cerium behaves like iron in the outer flame, 

but the inner flame yields a colorless or opaque yellow bead. 


- 


III, ALUMINIUM (Al). 


(a) WET REACTIONS. 
To be practised on a solution of common alum. 
p 


1. NH,HO ix presence of NH,Cl (group reagent) gives a gelatinous white pre- 
cipitate of aluminic hydrate—Al,(HO),. This precipitate is slightly 
soluble in a large excess of the precipitant, but separates completely 
on boiling. 

2. KHO and NaHO both give a similar precipitate, soluble in excess, but 
reprecipitated by boiling with an excess of ammonium chloride, or by 
neutralising with hydrochloric acid and boiling with a slight excess 
of ammonium hydrate. 

3. Na,HPO, zx the presence of NaC,H;,0, or NH4C,H;O, gives a white 
precipitate of aluminic phosphate—AlPO,—insoluble in hot acetic 
acid, but soluble in hydrochloric acid. The presence of citric or 
tartaric acids prevents the occurrence of this reaction. 


(4) DRY REACTION. 
(To be practised on dried alum.) 


Heat strongly on charcoal before the blowpipe, when a strong incandescence 
is observed, and a white residue is left. Moisten this residue with a drop of 
solution of cobaltous nitrate—Co(NO;)2—and again heat strongly, when a 
blue mass is left. ‘This test is not decisively characteristic, as other substances, 
such as zinc and earthy phosphates, show somewhat similar colors. 


CHROMIUM—MANGANESE. 21 





IV. CHROMIUM (Cr). 


(a) WET REACTIONS. 
(To be practised on a solution of potassium chromic chloride, prepared by 


dissolving potassium dichromate—K,Cr,O,;—in water, acidulating with 
hydrochloric acid, heating and dropping in alcohol till the solution turns 
green.) 


1. NH,HO ix the presence of NH,Cl (group reagent) precipitates green chromic 
hydrate—Cr,(HO),—slightly soluble in excess, but entirely reprecipi- 
tated on boiling. The presence of citric or tartaric acid interferes 
with the completeness of this reaction. 

2. KHO, or NaHO, gives similar precipitates, freely soluble in excess when 
cold, but entirely reprecipitable by continued boiling. 

3. Chlorinated soda—Na,0Cl,—or Plumbic peroxide—Pb0,—boiled with an 
alkaline solution of a chromium salt, produces a yellow solution of 
sodium chromate—Na,CrQO,. 

4. NaHPO, ix the presence of NaC,H,0, or NH,C,H,0, throws down pale 
green chromic phosphate—CrPO,—soluble when freshly precipitated 
=n excess of hot acetic acid, and freely soluble in hydrochloric acid. 
The presence of organic acids prevents this reaction. 


() DRY REACTIONS. 


1. Heated in the borax bead in the inner blowpipe flame, a fine green 
color is obtained. 

2. Fused on platinum foil, with a mixture of KNaCO, and KNO,, a yellow 
residue is obtained, consisting of chromates of the alkalies used. 
This mass is soluble in water, yielding a yellow solution turned deeper 
in color by the addition of hydrochloric acid, owing to the formation 
of dichromates, and becoming green on warming and dropping in 
rectified spirit. 


DIVISION B. 


Metals the hydrates of which, being soluble in excess of ammonium hydrate 
in the presence of ammonium chloride, escape precipitation by that reagent, 
but are separated as insoluble sulphides by the addition of ammonium sulphide 
to the same liquid. 


I. MANGANESE (Mn). v4 
(a) WET REACTIONS. (™ 


(To be practised on a solution of potassium manganous chloride, prepared by 
heating a solution of potassium permanganate with hydrochloric acid, and 
dropping in alcohol until a colorless solution is obtained.) 


1. NH,HS in the presence of NH,Cl and NH.HO (group reagent) precipitates 
a flesh-colored manganous sulphide—MnS—soluble in dilute and 
cold hydrochloric acid (distinction from the sulphides of Ni and 
Co). It is also soluble in acetic acid (distinction from zinc sulphide). 
This precipitate forms sometimes very slowly and only after gently 
warming. Ifa good excess of NH,Cl has not been added, or if, after 
adding the excess of ammonium hydrate, the solution be exposed to 
the air, a portion of the manganese will sometimes precipitate sponta- 
neously, as manganic dioxyhydrate— Mn,O,(HO),—and be found with 
the iron, etc., in the first division of the third group. In this case its 


22 DETECTION OF THE METALS. 
Sa ll 


presence will be easily made manifest during the fusion for chromium 
by the residue being green. It is therefore evident that small quan- 
tities of manganese cannot be perfectly separated from large quantities 
of iron by NH,Cl and NH,HO only. 

2. KHO and NaHO both yield precipitates of manganous hydrate insoluble 
in excess, and converted by boiling into dark brown manganic dioxy- 
hydrate—Mn,O,(HO),. 

3. NH,HO gives a similar precipitate, soluble in excess of ammonium chloride, 
but gradually depositing as Mn,O,(HO), by exposure to the air. For 
this reason, if the presence of manganese be suspected, the addition 
of NH,Cl and NH,HO must be followed by instant filtration, and any 
cloudiness coming in the filtrate must be simply taken as indicating 
manganese, and disregarded. 

4. K,FeCy, gives a precipitate of manganous ferrocyanide—Mn,FeCy,—very 
liable to be mistaken for the corresponding zinc compound. 

5. Boiled with plumbic peroxide and nitric acid a violet colour is produced in 
the liquid, due to the formation of permanganic acid. (Crum’s test.) 


(6) DRY REACTIONS. 


(To be practised upon manganese peroxide—Mn0O,,) 


1. Fused on platinum foil with KHO and a crystal of KCIO;, a green mass 
of potassium manganate is formed. This residue is soluble in water, 
yielding a green solution, turning purple on boiling, owing to the 
formation of potassium permanganate. The solution is rendered 
colorless by heating with hydrochloric acid and dropping in alcohol, 
the operation being accompanied by the odor of aldehyd. 

2. Heated in the borax bead in the outer blowpipe flame, a color is produced 
which is violet-red while hot and amethyst on cooling. The bead is 
rendered colorless by the reducing flame. 


II. ZINC (Zn). YL 
(2) WET REACTIONS. a, 
(To be practised on zinc sulphate—ZnSO,.) 
1. NH,HS in the presence of NH,Cl and NH,HO (group reagent) gives a white 


ro) 
precipitate of zinc sulphide—ZnS— insoluble in acetic acid, but readily 
soluble in dilute hydrochloric acid. 

2. KHO, NaHO, and NH,HO, ail give precipitates of gelatinous white zinc 
hydrate, soluble in excess to form zincates. The addition of sulphu- 
retted hydrogen or ammonium sulphide reprecipitates the zinc as zinc 
sulphide—ZnS. 

3. K,FeCy, gives a gelatinous white precipitate of zinc ferrocyanide— 
Zn,FeCy,—insoluble in dilute acids. 

4. Alkaline Carbonates precipitate ZnCO;(Zn2HO),H,O—zinc —hydrato- 
carbonate—insoluble in excess of the carbonates of potassium and 
sodium, but soluble in that of ammonium. The latter solution, diluted 
and boiled, deposits the oxide. | 


(6) DRY REACTIONS. 


(To be practised on zinc carbonate.) 


I. Salts of zinc heated leave the oxide yellow while hot, and white on 
cooling. . 


NICKEL—COBALT. 23 





2. Heated on charcoal before the blowpipe an incrustation forms, yellow 
while hot, and white on cooling. Moisten with a drop of cobaltous 
nitrate—Co(NO;),.—and again heat it in the outer flame, when a fine 
green color is produced. 


III. NICKEL (Ni). 


(2) WET REACTIONS. 
(To be practised on a solution of nickelous sulphate—NiSOu..) 


1. NH,HS in the presence of NH,Cl and NH,HO (group reagent) gives a black 
precipitate of nickelous sulphide—NiS—slightly soluble in excess, but 
entirely precipitated on boiling. It is not soluble in cold dilute 
hydrochloric or in acetic acid, but requires boiling with strong 
hydrochloric acid, and sometimes even the addition of a drop or two 
of nitric acid. 

2. KHO or NaHO both give a green precipitate of nickelous hydrate— 
Ni(HO),—unaltered by boiling (distinction from cobalt). 

3. Potassium nitrite—KNO,—added to a neutral solution, followed by an 
excess of acetic acid, gives no precipitate (after standing some hours) 
on the addition of potassium acetate and rectified spirit (very useful 
separation from cobalt). 

4. KCy in excess produces a greenish-yellow precipitate of nickelous cyanide 
—NiCy,—which quickly redissolves. On adding a drop of hydro- 
chloric acid and boiling in a fume chamber, and repeating this till no 
more fumes of hydrocyanic acid come off, and then adding sodium 
hydrate, a precipitate of nickel hydrate is produced. It is better, 
although less convenient, to use a strong solution of chlorinated soda 
in the last stage, when nickelic hydrate—Ni(HO),—is slowly pre- 
cipitated (separation from Co, which gives no precipitate). 

5. Alkaline Carbonates behave, so far as color and solubility in excess are 
concerned, like their respective hydrates. 


(6) DRY REACTIONS. 


1. Heated on charcoal with Na,CO, in the inner blowpipe flame, a grey 
metallic and magnetic powder is produced. 

2. Heated in the borax bead in the outer blowpipe flame, red to violet-brown 
is produced while hot, and a yellowish to sherry-red when cold. 
These colors might be mistaken for those of iron; but on fusing a 
small fragment of potassium nitrate with the bead, its color at once 
changes to blue or dark purple (distinction from Fe). 


IV. COBALT (Co). ame 
(a) WET REACTIONS. 
(To be practised on a solution of cobaltous nitrate—Co(NOs),.) 


1. NHS in the presence of NH,Cl and NH,HO (group reagent) gives a black 
precipitate of cobaltous sulphide—CoS—insoluble in acetic and cold 
dilute hydrochloric acid, and requiring to be boiled with the strongest 
HCl, often with the addition of a drop or two of nitric acid before 
solution is effected. 

2. KHO, or NaHO, gives a blue precipitate of cobaltous hydrate—Co(HO) .— 
rapidly changing to pink on boiling (distinction from nickel). 

3. KCy gives a light brown precipitate of cobaltous cyanide, rapidly soluble 


7 


24 DETECTION OF THE METALS. 





in excess, but reprecipitated by excess of dilute hydrochloric acid. If, 
however, the HCl be added drop by drop just so long as it causes 
the evolution of hydrocyanic acid fumes on boiling,* soluble potassium 
cobalticyanide—K,Co,Cy,,—results, which is not decomposed by 
hydrochloric acid; nor is any precipitate produced on adding excess 
of sodium hydrate or chlorinated soda (separation from nickel). 

4. Alkaline Carbonates throw down basic carbonates, behaving like the 
respective hydrates. 


(3) DRY REACTIONS. 


1. Heated on charcoal with Na,CO, in the inner blowpipe flame, the cobalt 
separates as a grey magnetic powder. 

2. Heated in the borax bead, first in the outer and then in the zmmer flame, 
a fine blue color is produced. It is an important distinction of cobalt 
from copper, manganese, etc., that prolonged heating in the inner flame 
does not affect this blue. 


GROUP IV. 


Metals the hydrates and sulphides of which, being soluble, are not precipi- 
tated by the addition of NH,HO and NH,4HS in the presence of NH,Cl, 
but separate as insoluble carbonates on the addition of ammonium carbonate 
to the same solution. 


I, BARIUM (Ba). 
(2) WET REACTIONS. ty 
(To be practised on a solution of barium chloride—BaCl,.) — 


1, Ammonium carbonate—(NH,),CO;—7x the presence of NH,Cl and NH,HO 
(group reagent) produces a white precipitate of barium carbonate— 
BaCO;—soluble with effervescence in dilute acetic acid. 

2. H,SO, and all soluble Sulphates give a white precipitate of barium sul- 
phate—BaSO,—insoluble in ammonium acetate or tartrate (distinction 
from PbSOx) and also in boiling nitric acid. 

3. K,CrO, gives a yellow precipitate of barium chromate—BaCrO,—insoluble 
in water and in dilute acetic acid, but soluble in hydrochloric acid 
(distinction from Sr and Ca). 

4. (NH,).0,0, gives a white precipitate of barium oxalate—BaC,O,—not 
readily formed in the presence of much acetic acid. 

5. Na,HPO, gives a white precipitate of barium hydrogen phosphate— 
BaHPO,—soluble in acetic acid, and to some extent in ammonium 
chloride. 


(6) DRY REACTION. 
(To be also practised on barium chloride. 


If a platinum wire be dipped first in hydrochloric acid and then in the salt, 
and held in the zzzer blowpipe or Bunsen flame, the outer flame is coloured 
yellowish-green. 
me 

* This must be done in a fume chamber, as it isa highly poisonous operation if the fumes 
should happen to escape into the room. 


STRONTIUM—CALCIUM. 25 


‘I, STRONTIUM (Sr). i 
(QE LT REACTIONS. 
(To be practised on strontium nitrate—Sr(NO3)..) 


1. (NH,),CO; (group reagent) in the presence of NH,C1 and NH,HO gives 
a white precipitate of strontium carbonate—SrCO3;—soluble in dilute 
acetic acid. 

2. H,S0O,, or a soluble sulphate (preferably calcium sulphate), yields a white 
precipitate of strontium sulphate—SrSO,—which only separates com- 
pletely from dilute solutions on allowing them to stand in a warm 
place for some hours. It is insoluble in a boiling strong solution of 
ammonium sulphate rendered alkaline by ammonium hydrate (distinc- 
tion from calcium sulphate). 

3. The other reactions are similar to those of calcium. 





(6) DRY REACTION. 
(To be also practised on Sr(NO3)9.) 


A platinum wire moistened with hydrochloric acid, dipped in the substance 
and introduced into the zzmer blowpipe or Bunsen flame, colors the outer 
flame crimson. 


III. CALCIUM (Ca). \v 
ia 
(a) WET REACTIONS. 


(To be practised on a solution of calcium chloride—CaC]l,.) 


1. (NH,),CO, in presence of NH,Cl and NH,HO (group reagent) produces a 
white precipitate of calcium carbonate—CaCO,—soluble in acetic acid 
and settling best on warming. | 

2. (NH,),C,04, precipitates white calcium oxalate—CaC,O,—insoluble in 
acetic or oxalic acids, but soluble in hydrochloric acid. 

3. H,SO, in strong solutions produces a precipitate of calcium sulphate— 
CaSO, Being slightly soluble in water, it does not form in dilute 
solutions, nor is it precipitated by a saturated solution of calcium 
sulphate (distinction from Ba and Sr). It is soluble in a boiling 
saturated solution of ammonium sulphate containing excess of ammo- 
nium hydrate, but quite insoluble in a mixture of two parts alcohol 
and one part water. 

. Na,HPO, produces a white precipitate of dicalcium phosphate—CaH PO, 

~ —soluble in acetic acid. 


BSS 


(3) DRY REACTION. 
(To be practised on calcium carbonate—CaCO3,) 


A platinum wire moistened with hydrochloric acid, dipped in the substance 
and held in the zzmer blowpipe or Bunsen flame, colors the outer flame 
yellowish-red. This reaction is masked by the presence of barium or 
strontium. 


26 DETECTION OF THE METALS. 





GROUP V. 


Metals not precipitable either as sulphide, hydrate, or carbonate, including 
magnesium the precipitation of which as hydrate or carbonate has been 
prevented by the presence of ammonium chloride. 


I. MAGNESIUM (Mg). 
(a) WET REACTIONS. 


(To be practised on a solution of magnesium sulphate—MgSO,.) 


1. Na,HPO, in the presence of NH4Cl and NH4HO produces a white crystalline 
precipitate of ammonium magnesium phosphate—MgNHy,PO,. It 
is slightly soluble in water, and scarcely at all in water containing 
ammonium hydrate, but entirely soluble in all acids. In very dilute 
solutions it only forms on cooling and shaking violently, or on rubbing 
the inside of the tube with a glass rod. 

2. (NH,),HAsO, produces a similar precipitate of magnesium arseniate— 
—MgN H,AsO,—possessing like features. 7 

3. KHO, NaHO, and NH,HO give precipitates of magnesium hydrate— 

, Mg(HO):—insoluble in excess, but soluble in the presence of 
ammonium salts. The alkaline carbonates (except ammonium car- 
bonate) precipitate magnesium carbonate, also soluble in ammonium 
salts. ; 

4. Calcium hydrate (dime water)—(CaHO),—and Barium hydrate (daryta water) 
—Ba(HO),— produce a similar effect. Either of these reagents is useful 
for the separation of magnesium from all the alkalies except ammonium. 
The solution, which must contain no ammonium salts, is treated with 
excess of either lime or baryta water. The precipitated magnesium 
hydrate is then filtered out and excess of ammonium carbonate added, 
which precipitates in turn the excess of Ca or Ba employed, and leaves 
K, Na, or Li in solution. 


} 


(3) DRY REACTION. 
(To be practised on magnesium oxide.) 


Heated on charcoal before the blowpipe, it becomes strongly incandescent, 
and leaves a white residue, which when moistened with a drop of solution of 
cobaltous nitrate—Co(NO;)2—and again heated, becomes rose-coloured. 
This test is not, however, infallible. 


I, LITHIUM (Li). 
(a) WET REACTIONS. 


(To be practised on a solution of lithium chloride, prepared by dissolving 
lithium carbonate in dilute hydrochloric acid.) 


1. Na,HPO, in strong solutions produce a white precipitate of lithium phos- 
phate—Li,PO,—on boiling only (distinction from Mg). It is soluble 
in hydrochloric acid, and reprecipitated by boiling with ammonium 
hydrate. 

2. Na,CO, and even NaHO, in very strong solutions, yield the carbonate and 
hydrate respectively. 

3. Platinic chloride—PtCl,—gives no precipitate (distinction from potassium). 


POTASSIUM—SODIUM—AMMONIUM. 27 





(6) DRY REACTION. 
(To be practised with lithium carbonate.) 


A platinum wire, moistened with hydrochloric acid, dipped in the substance 
and held in the zzmer blowpipe or Bunsen flame, colours the outer flame 
carmine red. ‘The presence of sodium disguises this reaction. 


III. POTASSIUM (K). 
WET REACTIONS. 


(To be practised on solution of potassium carbonate treated with dilute HCl 
till effervescence ceases, forming potassium chloride—KCl.) 


1. PtCl, in strong solutions, gives a yellow crystalline precipitate of potas- 
sium platino-chloride—K,PtCl,—soluble on great dilution, especially 
on warming, but insoluble in acids, alcohol, and ether. 

2. Hydrogen tartrate (¢artaric acid)—H,C,H,0,—throws down, from strong 
solutions only, a white crystalline precipitate of potassium hydrogen 
tartrate —KHC,H.O,—soluble in much cold water, rather freely in 
hot water, readily in acids and in KHO or NaHO, and not formed 
unless the original solution be nearly neutral. Its separation is facili- 
tated by stirring and shaking violently, in which case it settles quickly. ° 

3. Hydrogen silicofluoride (Aydrofluosilicic acid)—H,SiF¥ ,—yields white gela- 
tinous potassium fluosilicate —K,SiF,—sparingly soluble in water. 


) DRY REACTION. 
(To be practised on potassium carbonate—K ,CO;.) 


Dip a platinum wire, moistened with HCl, in the salt. Held in a Bunsen 
flame a violet color is imparted. The masking effect of Na (yellow) is 
obviated by viewing the flame through indigo glass. 


IV. SODIUM (Na). 
WET REACTIONS. 


(To be tested with solution of sodium chloride—NaCl.) 


1. KSb0, (fotassium metantimoniate) gives a white eranular precipitate of 
sodium metantimoniate—NaSbO,—from strong solutions only, which 
must be neutral or alkaline. This precipitate is insoluble in alcohol. 

2. H,SiF, gives a similar precipitate to that obtained with K salts in concen- 
trated solutions only. 

Sodium salts are, practically, all soluble in water, and there is no thoroughly 
trustworthy wet reaction which can be applied to detect small quantities. 
If we have a solution which gives no precipitate with any of the group 
reagents, but leaves, on evaporating, a fixed residue capable of imparting a 
strong yellow color to the Bunsen flame (dry reaction), we may infer with 
certainty the presence of sodium. 


V. AMMONIUM (NH,). 
WET REACTIONS. 


(To be tested with solution of ammonium chloride—N H,Cl.) 


. 1. PtCl, produces a heavy yellow precipitate of ammonium platino-chloride— 
(NH,),PtCl,—which, being rather soluble in water, is not formed in 


t 


28 DETECTION OF THE METALS. 


dilute solutions, unless alcohol, in which it is insoluble, be added in 
considerable quantity. When ignited, pure spongy platinum is left. 
This precipitate may be distinguished from that with K salts by adding, 
after ignition, a little water and AgNO,, when no white precipitate of 
AgCl is formed (the K salt leaves KCl on being strongly heated). 

2. H,C,H,0, yields ammonium hydrogen tartrate—(NH,)HC,H,O,—almost 
identical with KHC,H,O, in its properties. On ignition, however, the 
latter gives a black residue, which turns moistened red litmus paper 
blue (K,COs3 and C), the former leaving pure C without reaction. 

3. NaHO or Ca(HO), boiled with the solution causes the evolution of ammonia 
gas—NH;. ‘A glass rod dipped in HCl or HC,H,O, produces, when 
held over a mixture evolving NH3, white clouds (solid NH, salts), and 
moist red litmus paper is turned blue. 

4. Nessler’s Solution (HgI, dissolved in KI and KHO added) gives a 
yellow or brown color or a brown precipitate of dimercuric ammonium 
iodide—N(Hg"),I—with all NHy salts. This reaction is extremely 
delicate, and the estimation of NH, in water is founded upon it. 


DRY REACTIONS. 


Ammonium salts volatilise (1) with decomposition, leaving a fixed acid 
(¢.g., phosphate) ; (2) with decomposition, leaving no residue whatever (e.g., 
sulphate, nitrate) ; (3) without decomposition, when they are said to sublime 
(e.g., chloride, bromide, etc.) 


CHAPTER GLEE: 


DETECTION AND SEPARATION OF ACIDULOUS 
RADICALS. 


1, HYDROFLUORIC ACID and FLUORIDES. 
(The test for fluorides undernoted may be practised on fluor spar—CaF;.) 


Hydrofluoric Acid, or Fluoric Acid, is known— 

1. By its strongly acid reaction and corrosive power. 

2. By its action upon glass, from which it dissolves out silicic acid— 
SiO,—thus roughening the surface and rendering it semi-opaque 
or translucent, and white; a colorless gas, silicic fluoride— 
SiF,—passing off. 

Fluorides are detected as follows :— 

The mineral or salt is finely powdered, and introduced into a leaden dish 
with a little sulphuric acid. A piece of glass, previously prepared by coating 
its surface with wax, and etching a few letters on the waxed side with the 
point of a pin, is placed over the dish, waxed side down. A gentle heat is 
then applied, but not sufficient to melt the wax, and the operation continued 
for some time. The glass is then taken off, and the wax removed from it; 
when, if fluorine was present, the letters written on the waxed surface will be 
found engraved upon it by the action of the hydrofluoric acid. 


2. CHLORINE, HYDROCHLORIC ACID, and CHLORIDES. 


Free Chlorine—Cl,—may be detected— 
1. By its odor. 
2. By turning paper dipped in solution of potassium iodide brown. 
3. By bleaching a solution of indigo or litmus. 


Hydrochloric Acid—HCl—may be recognised— 
1. By its acidity and odor of its fumes. 
2. By producing dense white fumes when a rod dipped in ammonium 
hydrate is held over the mouth of the bottle. 
3. By giving a curdy white precipitate of argentic chloride with argentic 
nitrate, instantly soluble in ammonium hydrate. 


Chlorides give the following reactions (to be practised with any soluble 
chloride, say NaCl) :— 
1. Heated with sulphuric acid they evolve white fumes of HCl. 
2. Heated with H,S0, and MnO, they evolve chlorine. 
3. AgNO, ix the presence of HNO; gives a white precipitate of argentic 
chloride—AgCl—insoluble in boiling nitric acid, but instantly 
soluble in dilute ammonium hydrate of a strength of 1 in 20. 


30 DETECTION, £TC., OF ACIDULOUS RADICALS. 





4. The solid substance mixed with K2Cr,O, and distilled with H,SO, 
yields chloro-chromic oxide—CrCl,0,—in red fumes which, when 
passed into dilute ammonium hydrate, color it yellow, owing 
to the formation of ammonium chromate—(NH,),CrO,. The 
yellow should change readily to green on the addition of a 
few drops of sulphurous acid. 


Insoluble Chlorides should be first boiled with strong sodium hydrate and- 
the whole diluted and filtered. The chloride is then transferred to the 
sodium, and is to be searched for in the filtrate by acidulating with nitric acid 
and adding argentic nitrate, as above described. 


&, HYPOCHLORITES. 
(Practise on a solution of chlorinated lime—CaOCl,). 


Hypochlorites are all readily soluble in water, are contained in the so-called 
chlorinated compounds, and are recognised— 
1. By having an odor of chlorine. 
2. By giving a blue with potassium iodide, starch paste, and acetic acid, 
due to liberation of chlorine. 


4. CHLORATES. 
(To be practised on potassium chlorate—KCIO,.) 


1, Heated on charcoal, they deflagrate. 

2. Heated with strong sulphuric acid, they evolve chlorine peroxide— 
Cl,04.—which is yellow and explosive. 

3. Their solutions yield no precipitate with argentic nitrate; but if a 
little of the solid be heated to redness, and the residue dissolved - 
in water, a precipitate of argentic chloride is obtained. The 
same reduction from chlorate to chloride may also be effected 
by adding zinc and dilute sulphuric acid to the solution. 

4. Mixed with KI and starch paste, and acidulated with acetic acid, 
they give no blue (distinction from hypochlorites), but on 
adding HCl a blue is developed. 


5. PERCHLORATES. 


These are distinguished from chlorates— 
1. By giving off perchloric acid—HClO,—when heated with sulphuric acid, 
without explosion or evolution of chlorine peroxide. 
2. Like chlorates, they require reduction to chlorides before giving a precipitate with 
argentic nitrate, 


6. BROMINE, HYDROBROMIC ACID, and BROMIDES. 


Bromine—Br,—is distinguished— 
1. By its appearance—heavy, reddish-brown liquid, giving off reddish 
fumes of a very penetrating, unpleasant odor. 
2. By turning starch paste yellow or pink. 
3. When present in small quantity in solution, on adding a few drops 
of chloroform and shaking, an orange color is imparted to 
that liquid, which sinks to the bottom of the aqueous solution. 


Hydrobromie Acid—HBr—is known— 


By its acid reaction and the production of fumes of bromine when 
heated with strong sulphuric acid. 


BROMIDES—IODIDES. 31 





Bromides are all soluble in water, except the silver, mercurous, and lead salts ; 
they are detected by the following characters (to be practised 
on potassium bromide—K Br) : 

1. Heated with strong sulphuric acid, they evolve red vapors of 
bromine. 

2. A similar effect is produced by sulphuric acid and metallic 
dioxides, such as PbO,, MnO,. 

3. Mixed with starch paste, and a few drops of chlorine water 
carefully added, they give an orange color (starch bromide). 

4. Mixed in a long tube with chloroform, and a few drops of chlorine 
water added, the whole, when shaken well together, leaves a 
characteristic reddish-colored stratum at the bottom of the 
liquid in the tube, due to free bromine in the chloroform. 

5. With argentic nitrate they give a dirty-white precipitate of argentic 
bromide, insoluble in nitric acid, slowly soluble in ammonium 
hydrate, but insoluble in dilute NH,HO, of a strength of 1 in 20 
(argentic chloride dissolves). 

6. Distilled with potassium dichromate and sulphuric acid, red fumes 
are evolved, which give no color when passed into ammonium 
hydrate (distinction from chlorides). 


Insoluble Bromides should be first boiled with NaHO, as described under 
insoluble chlorides. 


7. HYPOBROMITES, 


These are very similar to hypochlorites, and react as follows :— 
I. They decompose by heat, leaving a bromide ; 
2. On boiling with an alkali, a mixture of bromide and bromate results. 


8. BROMATES. 


These are recognised— 
1. By deflagrating on charcoal, leaving the corresponding bromide. 
2. By liberating bromine on the addition of dilute sulphurous acid. 


9. IODINE, HYDRIODIC ACID, and IODIDES. 


Iodine—I,—is readily known by its glistening black scales, its odor, the 
violet vapor on heating, and the production of blue iodide of starch on 
adding a solution to starch paste. 


Hydriodic Acid—HI—in the gaseous state, is known by the formation 
of a brown color on holding paper moistened with chlorine water (blue if 
also dipped in starch paste) over a tube in which it is being evolved. 


Todides are readily known by the following reactions (which may be 
practised on a solution of potassium iodide, KI) :-— 

1. Heated with strong sulphuric acid they give a liberation of iodine 
with violet fumes. 

2. Mucilage of starch and chorine water or strong nitric acid (if not 
added too plentifully) produces blue iodide of starch, decom- 
posed by heat, but re-formed on cooling; also destroyed by 
excess of Cl (iodine trichloride—ICl,—being produced). 

3. The light yellow precipitate of argentic iodide —AgI—formed when 
a solution (containing alkaline metals only) is added to 
argentic nitrate dissolved in water. The precipitate, when 
freed from the supernatant liquid, does not dissolve in hot 
HNOs, and is practically insoluble in ammonium hydrate, 
being thus distinguished from a chloride. 


32 DETECTION, ETC., OF ACIDULOUS RADICALS. 


A 


4. A neutral solution (produced, if alkaline in the first place, by the 
cautious addition of dilute HNO;; if acid, by dropping in 
KHO solution until test-paper is unaffected) gives with one 
part of cupric sulphate—CuSO,—and three parts, or rather 
less, of ferrous sulphate—FeSO,—dissolved in a little water, 
a greyish precipitate of cuprous iodide—(Cu,)'T’s. 

The same precipitate is produced if sulphurous acid—H,SO; 
—be used with the cupric sulphate instead of ferrous sulphate. 

s. Palladious Chloride—PdCl,—or palladious nitrate—Pd(NO;),— 
gives a black precipitate of palladious iodide—PdI,—decom- 
posed somewhat below the temperature of boiling mercury, 
iodine being evolved, and the metal left. This is a very 
expensive but efficient separation. 

6. Mercuric chloride and plumbic nitrate give respectively red and 
yellow precipitates with soluble iodides. 


10. IODATES. 


(Practise on solution of potassium iodate—KIO;.) 
Iodates are known— 

1. By giving, when heated with strong sulphuric acid, effects likely to be mistaken 
for chlorates. 

2. By giving a blue with starch paste on the addition of sulphurous acid. 

3. By giving a blue with starch paste on the addition of potassium iodide and 
tartaric acid. 

4. By yielding a precipitate of ferric oxy-iodate on adding ferric chloride. 


11. PERIODATES, 


Periodates are distinguished— 

1. By giving a precipitate with BaCl,, in a neutral solution, which is not decomposed 
by digesting with ammonium carbonate and a little NH,HO. Iodates leave 
barium carbonate, which when washed dissolves in acid with effervescence. 

2. By adding Hg(NO,), and treating the yellowish precipitate with SnCl,. It turns 
green, HgI, being produced. 


12, WATER and HYDRATES. 


Water is recognised— 

1. By its absolute neutrality to test-paper. 

2. By its evaporating without residue, fumes, or odor of any kind. 

3. By its turning white anhydrous cupric sulphate blue. 

4. By its yielding pure hydrogen when boiled and the steam passed 
slowly over copper turnings heated to bright redness in an iron 
tube. 

s, By its undergoing electrolysis, and yielding hydrogen at the negative 
and oxygen at the positive electrode. — 


The soluble Hydrates, viz, KHO, NaHO, LiHO, Ba(HO),, Sr(HO),, and 
Ca(HO), are known— 
1. By being more or less soluble in cold water, yielding solutions 
which are strongly alkaline to test-paper. 
2. By dissolving in hydrochloric acid without effervescence and without 
smell. 
3. By giving a brownish-black precipitate of argentic oxide—Ag,O— 
with argentic nitrate. 
The insoluble Hydrates are recognised— 
By giving off steam when heated in a dry test-tube, and leaving a 
residue which behaves like the corresponding oxide. 


OXIDES—SULPHIDES. 33 


a eee ———————E——— Taran etd 


13. OXIDES. 


_ All oxides are insoluble in water. Oxides of K, Na, Li, Ba, Sr, and Ca 
unite with water to form hydroxides, which dissolve with a greater or less 
degree of readiness and give the characters of the soluble hydrates already 
mentioned. 


Normal Oxides can only be recognised by negative results, such as :— 

1. Heated alone, they are not changed ; except argentic oxide, which 
leaves the metal, and mercuric oxide, which volatilises and ~ 
breaks up into the metal and oxygen. 

2. They are insoluble in water (exceptions K, Na, etc., as above), but 
soluble in hydrochloric or nitric acid without effervescence and 
without smell. 

3. After dissolving and removing the metal by H,S or Na,CO3 as 
most convenient, no acidulous radical is found, other than that 
of the acid used to dissolve. 

4. Boiled with strong NaHO and filtered, or fused with KNaCO, and 
digested with water, the solution gives no reaction for any acid 
radical except the soluble hydrate or carbonate employed. 


Peroxides, on account of their containing an excess of oxygen, differ from 
normal oxides (practise on MnO,),— 
1. By giving off oxygen when strongly heated. 
2. By evolving chlorine when heated with hydrochloric acid. 


14. SULPHUR, HYDROSULPHURIC ACID, and SULPHIDES. 


Ordinary Sulphur—s, or S,—is recognised— 

1. By its burning entirely away with a pale blue flame, and evolving 
sulphurous anhydride. __ 

2. By its insolubility in all ordinary menstrua, such as water, alcohol, 
and ether, but dissolving readily in carbon disulphide. 

3. When slowly heated in a tube, it first melts, then thickens, then 
melts again, and finally boils, the vapor taking fire and forming 
sulphurous anhydride. 


Precipitated Sulphur possesses the above characters, and is specially distin- 
guished from ordinary sulphur by being quite amorphous under 
the microscope, while the latter is crystalline. by 


Hydrosulphuric Acid—H,S (sulphuretted hydrogen)—is known— 
1. By being acolorless gas with a disgusting odor of rotten eggs, and 
inflammable, burning in the air to produce sulphurous acid. 
2. By turning a piece of paper black, which has been moistened with 
solution of plumbic acetate and held over the mouth of the 
tube or jet from which it issues. 


Normal Sulphides are divisible into five classes :— 

1. Soluble in water, including the sulphides of K, Na, Nig Cason 
Ba, and Mg. 

2. Insoluble in water, but readily soluble in dilute hydrochloric acid, 
including those of Fe, Mn, Zn. 

3. Insoluble in dilute, but soluble in strong boiling hydrochloric acid, 
including the sulphides of Ni, Co, Sb, and Sn (PbS is also 
slightly affected, but separates on cooling, as chloride). 

4. Insoluble in hydrochloric acid, but attacked by strong heated nitric 
acid, being converted wholly or partially into sulphates. These 
include the sulphides of Pb, Ag, Bi, Cu (arsenious sulphide is 
slowly affected). 


©) 


34 DETECTION, £TC., OF ACIDULOUS RADICALS. 





5. Not dissolved by any single acid, but converted into a soluble 
sulphate by the action of nitro-hydrochloric acid, or hydro- 
chloric acid and potassium chlorate ; including those of 
Hg, As, Au, and Pt. 

Sulphides soluble in water or in hydrochloric acid are recognised (practise 
on soln ngy of NaS)— 
1, By giving off sulphuretted hydrogen when heated with HCl, which 
gives the smell and reactions already noted. 

2. Soluble sulphides precipitate solutions of lead and cadmium, black 
and yellow respectively. 

3. Soluble sulphides give a purple colour with sodium nitroprusside— 
Na,Fe(NO)C;N;—only after the addition of a soluble hydrate. 


Sulphides insoluble in hydrochloric acid are best detected (practise on 
ranallionis 
. By heating with strong nitric or nitro-hydrochloric acid, diluting 
the solution, and testing for a su/phate with barium chloride 
(see page 36). 

2. By fusion with KNaCO, and KNOsg, digesting the residue in water, 
filtering and testing the solution for a sw/phate,—formed by the 
oxidising action of the potassium nitrate. 

3. Mix a little with sodium carbonate and borax, and heat on charcoal 
before the blowpipe. Remove the mass thus obtained, place 
it on a clean silver coin, and moisten with a drop of distilled 
water ; when, owing to the formation during ignition of sodium 
sulphide—Na,S,—a black stain of argentic sulphide—Ag,S— 
will be produced. 


Polysulphides as commonly met with are those of the alkalies, and are 
soluble in water. They are known (practise on sulphurated potash—K,S,)— 

1. By the deep yellow or orange color of their solutions. 
2. By evolving sulphuretted hydrogen accompanied by a deposit of 
sulphur when treated with hydrochloric or dilute sulphuric acids. 
The polysulphides which are insoluble in hydrochloric acid, such as iron 
pyrites, copper pyrites, etc., are best proved by fusion with potassium nitrate 
and carbonate and conversion into sulphate. ‘They may, however, be recog- 
nised by heating with hydrochloric acid and zinc, when the excess of sulphur 

will pass off as H,S, leaving the normal sulphide. 


15. THIOSULPHATES (Hyposulphites). 
(Practise on solution of commercial hyposulphite of soda—Na,.S,035 H,O.) 


These salts, commonly known as hyposulphites, are usually soluble in water, 
and exhibit the following characters :— 

1. With either dilute or strong HCl and H,SQ,, they give off SO, 
and form a yellow deposit of S (distinction from sulphides, 
polysulphides, and sulphites). 

2. AgNO, gives no precipitate at first, owing to excess of a hypo- 
sulphite dissolving argentic hyposulphite—Ag,S,O,,—but on 
continuing the addition, this AgeS2Os is precipitated of a white 
color. The salt splits up spontaneously, becoming yellow, 
-brown, and lastly black, and being changed completely into 
argentic sulphide—Ag,S. The same decomposition of the 
precipitate occurs on substituting HgNO,; or Pb(NOs), for 
AgNO3; and in all three cases heat accelerates the action, 
and H,SO, is the by-product. 


SULPHITES AND SULPHATES. 35 





3. Fe,Cl, produces a reddish-violet color, gradually disappearing as 
FeCl, is formed. (Zhis color ts not produced by sulphites, and 
a somewhat similar tint produced by Fe,Cl, in thiocyanates does 
not disappear.) 

4. Na,OCl, or Cl, water converts hyposulphites into sulphates, even 
without applying heat. 


16. SULPHUROUS ACID and SULPHITES. 
Sulphurous acid—H,SO,—is recognised in solution— 

1. By its pungent odor of burning sulphur, due to evolution of SO,, 
which gas combines directly with peroxides to form sulphates. 
For instance :-— 

PbO, + SO, = PbSOx,. 
(This reaction is utilised in gas analysis, to separate SO from a 
mixture.) 

2. By adding barium chloride in excess, filtering out any precipitate 
of barium sulphate which may form (owing to the fact that 
all samples of the ordinary acid contain sulphuric acid), and 
then adding chlorine water and getting another copious white 
precipitate of barium sulphate, owing to the conversion of the 
sulphurous into sulphuric acid by the oxidising action of the 
chlorine water, thus :— 

H,SO, + BaCl, + Cl, + H,O = BaSO, + 4HCl. 

3. Treated with zinc and hydrochloric acid, it evolves sulphuretted 

hydrogen, thus :— 
3Zn + 6HC] + H,SO3 = 3ZnCl, + HS + 3H,0O. 

4. When a solution of iodine is dropped into the liquid, its color is 
discharged, owing to its conversion into hydriodic acid by the 
hydrogen of the water, the oxygen of which passes at the same 
time to the sulphurous acid, forming sulphuric acid. 

fa. + lo + H.O = H.s0;, + 2HI 
Sulphites are known by the following characteristics (practise on solution 
of sodium sulphite—Na,SO3) :— 

1. All except the alkaline sulphites are sparingly soluble in water. 

2. When heated with sulphuric acid they evolve sulphurous anhydride, 
without deposit of sulphur. 

3. Acted on with zinc and hydrochloric acid, they evolve sulphuretted 
hydrogen, which blackens a piece of paper moistened with 
plumbic acetate and held over the mouth of the test-tube. 

4. A salt of silver, mercury, or lead produces a precipitate which on 
heating turns dark, owing to the formation of a sulphide and 
free sulphuric acid. 

5. By boiling with barium chloride and chlorine water or nitric acid, 
barium sulphate is produced, and precipitates. 

6. K,Cr,O, and HCl give a green coloration of chromic sulphate 
or chloride. ‘This test is very delicate, but by itself is not 
conclusive, as any reducing agent acts similarly. — 


17. SULPHURIC ACID and SULPHATES. 
The acid—H,SO,—is detected— 
1, By its appearance. A heavy, oily, odorless, and nearly colorless 
liquid, powerfully acid and corrosive. 
2. By its charring effect. This is made evident when the strong acid 
is dropped upon white paper, wood, etc., or when the dilute 
acid is evaporated in a basin containing a little white sugar. 


36 DETECTION, ETC., OF ACIDULOUS RADICALS. 





The carbonisation is due to the power the acid has of abstract- 
ing the elements of water from organic bodies. 

3. By liberating an explosive gas when dropped on a small fragment of 
KCI1O3. 


Sulphates are soluble in water, with the exception of daszc sulphates (soluble 
in acids) and BaSO,, SrSOz, CaSO,, and PbSO4. (Ag,SOx is only slightly 
soluble.) When those insoluble in dilute acids are required to be analysed, 
they are decomposed either by boiling with potassium or sodium hydrates or 
by ignition with KNaCOs, the latter being preferable. The sulphate radical, 
being brought into combination with K or Na to form a soluble sulphate, is to 
be tested for in the filtrate after boiling with water. Sulphates are recognised 
by the following characters (practise on solution of magnesium sulphate) :— 

1. BaCl, or Ba(NOs), produces a white precipitate of barium sulphate 
—BaSO,— insoluble in boiling water and also in boiling nitric 
acid. The addition of barium chloride to a strongly acid 
solution often causes the reagent to crystallise out, and this 
is then mistaken by the student for a true precipitate of 
sulphate ; therefore the boiling water should always be em- 
ployed. 

2. The addition of a soluble salt of lead or strontium also causes the 
formation of insoluble sulphates ; but these reactions are never 
in practice used, the barium chloride being at once the most 
delicate and serviceable reagent. 

3. Heated with a little Na,CO, on charcoal in the inner blowpipe 
flame, sulphates are reduced to sulphides ; and the residue, placed 
on a clean silver coin and moistened with water, leaves a black 
stain. 


18. CARBON, CARBONIC ACID, and CARBONATES. 


Carbon—C,— is known— ) 
1. By its black color and by burning in the air and producing a gas 
which is odorless, so heavy that it can be poured from one 
vessel to another, and causes a white precipitate when passed . 
into solution of calcium hydrate. 
2. By its capability of removing many vegetable coloring matters 
from their solutions. 


Carbonic Acid—H,CO3;—is not known in the free state, splitting up into 
carbonic anhydride—CO,—and water. CO, is recognised— 

1. By being odorless and giving white insoluble CaCO, (or BaCOs) 
when passed into a solution of Ca(HO), or Ba( HO). 

2. By turning blue litmus purple or wine-red, the original tint being 
restored by heat, the CO, escaping. 

Carbonates are mostly insoluble in water, the alkaline carbonates alone 
dissolving. CaCO3, SrCO3, BaCOs, and MgCOs (also MnCO 3 and FeCOs) 
dissolve in water containing CO, (especially under pressure), forming bicar- 
bonates or hydrogen carbonates, from which CO, passes off on boiling. All 
carbonates give off CO, on ignition, except K,CO3 and Na,CO3. A white 
heat is needed to decompose BaCO3 and SrCO;. Most carbonates on heating 
to redness leave the oxide. Their recognition depends upon (practise upon 
calcium carbonate)— 

1. Effervescing with a solution of almost any acid (H,S and HCy 
excepted), organic or inorganic, and giving off an odorless 
gas—CQ,. 

2. When the gas given off is poured or passed into a solution of 


~ 


BORIC ACID, BORATES, AND SILICATES. 37 


aan tea 


calcium hydrate, a white precipitate of CaCOs falls, which dis- 
solves on continuing to add CO,. When the gas given off has 
the odor of H,S or SO,, either of these may be removed by 
passing through K,CrO, and HCl, which is rendered green, 
and the unacted-upon CO, is allowed to pass into calcium 
hydrate solution as before. 

3. HgCle gives a reddish-brown precipitate with the carbonates of 
K, Na, and Li, and a white one with bicarbonates of the same 
metals. 

4. Soluble carbonates give a white precipitate with cold solution of 
MgSO,, while bicarbonates do not. 


19. BORIC ACID and BORATES. 


Boric (or Boracic) Acid—H;BO0;—is distinguished as under :— 

1. It is a white crystalline solid, giving off water on being heated, and 
leaving the anhydride—B,O3. 

2. When warmed with alcohol, a gveen flame is produced on applying 
a light to the latter. 

3. When dissolved in hot water, and a piece of turmeric paper dipped 
in the solution, the yellow color is unaffected ; but upon drying 
the paper it becomes brownish-red, turned green on moistening 
with KHO. 

All borates dissolve in dilute acids, but few in water, and when 
decomposed by hot acids, let fall crystalline boric acid on 
cooling, which answers to the above characters. 


The presence of soluble borates is detected by the following tests (practise 
upon borax—Na,B,O,10H,O :— 

1. They give, on heating with calcium chloride, rendered slightly 
alkaline with ammonium hydrate, a white precipitate of calcium 
borate, soluble in acetic acid, and so distinguished from oxalate. 

2. On rendering the solution just acid with hydrochloric acid, it reacts 
with turmeric paper as does H3BO3. 

3. Besides these two tests, which are in themselves, taken together, 
quite conclusive, borates give a white precipitate with argentic 
nitrate soluble in nitric acid. 

4. When a little of the solid borate is moistened with a drop of 
sulphuric acid, and alcohol is added, the green flame of 
H;BO3 is obtained on applying a light. 


20. SILICIC ACID and SILICATES. 


The acid H,SiO, is scarcely ever met with, and we have practically to deal 
with the anhydride—SiO,—which is totally insoluble in water and dilute acids, 
the acid dissolving slightly in both. SiOx is characterised— 

1. By its infusibility when heated. 

2. By its insolubility in water and all acids except HF. 

3. By forming, when heated with H.SO, and CaF, in a leaden vessel, 
gaseous silicic fiuoride—SiF .—which deposits the acid— H,Si0, 
—and forms hydro-fluosilicic acid—H,SiF,—in contact with 

: moisture. 

Silicates are not as a rule soluble in water, K,SiO, and Na,SiO, being the 
only ones thus affected, especially when much KHO or NaHO is present. 
Many of them do not dissolve in strong acids (a few are decomposed by hot 
H,SO,, but by no other acid), but all are split up by the action of gaseous 
hydrofluoric acid or a mixture of CaF, and H,SO,. 

1. On adding HCl to a soluble silicate, H,SiO, falls as a gelatinous 


38 DETECTION, ZTC., OF ACIDULOUS RADICALS. 





—scarcely visible—precipitate, slightly soluble in water. On 
evaporating to dryness and heating to 280° or 300° Fahr., the 
addition to the residue of a little HCl and water leaves the SiO, 
as a white gritty powder. 

2. NH,Cl precipitates H,SiO, from a soluble silicate. 

3. Silicic anhydride is separated from all acidulous and basylous 
radicals by fusing the finely powdered insoluble silicate with 
Na,CO, (or fuston mixture), in a platinum crucible ; boiling with 
water, filtering, evaporating nearly to dryness, adding dilute HCl 
until the whole is acid, re-evaporating, and, when dry, heating 
to 280° or 300° Fahr. On adding a little HCl, SiO, alone 
remains insoluble. 


21. HYDROFLUOSILICIC ACID (H,SiF,). 


This acid is only known in solution. 

1. It is very acid, and dissolves metals with the evolution of hydrogen, forming 
silico-fluorides which decompose by heat, leaving fluorides, and giving off 
silicon fluoride—SiF,. 

2. It gives off hydrofluoric acid when evaporated, and should not, therefore, be 
heated in glass vessels, as they would be etched. 

3. The majority of silico-fluorides are soluble, the exceptions being K,SiF,, 
BaSiF, and Na,SiF,, which are insoluble, especially in presence of a little 
alcohol. 


4. It does not precipitate strontium salts, even from strong solutions, but throws 


down BaSiF, on adding BaCl, and alcohol, as a white translucent crystalline 
precipitate. 


5. Potassium salts throw down gelatinous K,SiF,. 


22. NITROUS ACID AND NITRITES. 


Nitrous Acid (so called commercially) is nitric acid containing nitrous 
anhydride. It is yellowish in color, and evolves reddish fumes. 


Nitrites are all soluble in water, the least so being argentic nitrite. They are 
known as follows (practise upon potassium nitrate which has been heated 
to dull redness or upon sodium nitrite—NaNO,) :— 

1. They give red fumes when treated with strong sulphuric acid. 

2. They give an instantaneous blue color with potassium iodide and 
starch paste on the addition of a few drops of dilute sulphuric 
acid. The sulphuric acid liberates hydriodic acid from the 
iodide, and nitrous acid from the nitrite; the hydriodic acid 
is decomposed by the nitrous acid into iodine, water, and nitric 
oxide :— 


2HNO,+ 2HI=I,+2H:0+2NO. 


[Nitrazes, it must be remembered, would give frequently a similar reaction after 
standing, through the possible reduction of some portion of their nitric acid 
to nitrous acid ; so that unless the reaction appears instantly, and is confirmed 
by others, it is not safe to rely upon it as a test.] 


3. They give a dark brown color with ferrous sulphate zw¢thout the 
previous addition of sulphuric acid, as required by nitrates. 

4. Potassium dichromate in solution is converted into a green liquid 
by the addition of a nitrite and an acid. These two latter 
substances also reduce solution of auric chloride, forming a 
precipitate of the metal, possessing a dark colour. | 


- 


NITRIC ACID AND NITRATES. 39 


EEE —E———EE— Ee a aca eee 


23. ‘NITRIC ACID and NITRATES. 


Nitric Acid—_HNO;—is strongly acid and corrosive, fumes in the air, and 
readily dissolves most metals. It may be at once recognised by the following 
characters :— 

t. When poured on a piece of copper foil, and a piece of white paper 
held behind the test-tube, it is observed to be filled with’ 
orange-red fumes of nitric peroxide—N,Q,. 

2. When dropped on a piece of quill in a basin, or, if the solution be 
weak, when evaporated in contact with the quill, the latter is 
stained yellow. This stain is intensified to orange on adding 
an alkali, and is not discharged by warming, both of which 
decolourise the corresponding stains produced by iodine and 
bromine. — 

3. Dropped on a few crystals of brucine, a deep red colour is 
produced. 


Nitrates are characterised by the following properties (practise upon solution 
of potassium nitrate—KNOs) :— 

rt. All nitrates are soluble in water, especially when slightly acidulated 
with nitric acid. The nitrates of the alkalies are only decom- 
posed by a very high temperature, but most of the nitrates 
of the heavy metals, such as copper, mercury, and lead, when 
heated are readily decomposed, leaving a residue of oxide. 
Argentic nitrate, however, when heated leaves metallic silver. 

2. When heated with sulphuric acid they evolve pungent fumes of 
nitric acid. 

3. When heated with sulphuric acid and a piece of copper wire, they 
produce red fumes of nitric peroxide (caused by the union of 
the nitric oxide evolved with the oxygen of the air). 

4. When mixed with a solution of ferrous sulphate in the presence of 
sulphuric acid, a black coloration is produced, which is due to 
the production of nitric oxide, and its absorption by the ferrous 
salt. On heating, the colour disappears, and the ferrous is 
changed to the ferric sulphate. 


Note.—There. are two ways of applying this test :— 3 
(a) Place a drop or two of the solution on a white porcelain slab or crucible lid, and 
having added a drop of strong sulphuric acid, put a small and clean crystal 
of the ferrous sulphate in the liquid, when a black ring will gradually form 


round the crystal. 

(2) Place the solution in a tube, and having added some strong solution of ferrous 
sulphate, cautiously pour some strong sulphuric acid down the side of the 
tube, so that it sinks to the bottom by reason of its great gravity without 
mixing with the fluid. If nitric acid be present, a dark line will be formed 
at the junction of the two liquids. 


5. Treated with sulphuric acid, and a few drops of indigo sulphate 
added, the blue color of the latter is destroyed, being changed 
to yellow (not characteristic). 3CisHigN,O» (INDIGOTIN) + 
4HNO3=6C,H;NO, (Isatin) + 4NO + 2H,0. 

6. The most delicate test for nitrates is, however, phenyl-sulphuric 
acid. This reagent is prepared by dissolving one part of 
carbolic acid in four parts of strong sulphuric acid, and then 
diluting with two parts of water. A few drops of the solution 
to be tested are evaporated to dryness on a porcelain crucible 
lid over the water bath, and while still over the bath a drop of 
the reagent is added, when a reddish color is immediately 
produced, owing to the formation of nitro-phenol. 


40 DETECTION, ETC., OF ACIDULOUS RADICALS. 





24. CYANOGEN, HYDROCYANIC ACID, and CYANIDES. 


Cyanogen—CN or Cy—is a colorless gas, which is recognised— 
1. By its odor of bitter almonds. : 
2. By its burning in the air with a peach-blossom-colored flame, pro- 
ducing carbonic anhydride and nitrogen. 


Hydrocyanic Acid—-HCy—is volatile, soluble in water, and possesses a 
characteristic faint sickly odor of almonds. Its reddening action on litmus 
paper is very transient. Its tests are four in number, as follows :— 

1. Zhe Silver Test.—Argentic nitrate added to a solution of prussic 
acid gives a curdy white precipitate of argentic cyanide. The 
precipitate is soluble in ammonium hydrate and in strong boil- 
ing nitric acid, but not in dilute nitric acid; nor does it blacken 
on exposure to the light. 

2. Scheele’s [ron Test.—An excess of solution of potassium hydrate is 
mixed with the solution. To this a mixture of a ferrous and a 
ferric salt is added, and the whole acidulated with hydrochloric 
acid. If hydrocyanic acid be present, Prussian blue will be 
formed. 


The explanation of the test is as follows (according to Gerhardt’s view) :— 

(1) The hydrocyanic acid and the potassium hydrate form potassium cyanide. 

(2) The addition of the ferrous salt produces ferrous cyanide. 

(3) This reacting with the excess of alkali forms potassium ferrocyanide. 

(4) On the addition of the ferric salt, it is at first precipitated by the excess of alkali, 
as ferric hydrate, which on acidulation dissolves to ferric chloride, forming 
ferric ferrocyanide (Prussian blue). 


(i.) 6HCy + 6KHO = 6KCy + 6H,0. 
(ii) 6KCy + 3FeCl, = 3FeCy, + 6KCL. 
(iii.) 3FeCy, + 4KHO = K,FeCy, + 2Fe(HO)>. 
(iv.) 3K,FeCy, + 2Fe,Cl, = (Fe,)4(FeCy,), +12 KCl. 
Or the whole may be shown in one equation, thus, which is quite sufficient :—- 
18KCy + 3FeCl, + 2Fe,Cl, = (Fe,),(FeCy,)3 + 18 KCL. 

3. Lhe Sulphur Test—A few drops of ye//ow ammonium sulphydrate 
is added to a solution of hydrocyanic acid, and the whole 
evaporated to dryness at a very gentle heat, with the addition 
of a drop of ammonium hydrate. A residue is thus obtained 
which (when cold) strikes a blood-red color with ferric 
chloride, not dischargeable by hydrochloric acid, but at once - 
bleached by solution of mercuric chloride. 

This color is due to the formation of ammonium sulphocyanide (which takes 


place when an alkaline sulphide, containing excess of sulphur, is brought 
into contact with cyanogen)— 


2HCy + (NH,),S + S,=2NH,CyS + H,S, 
and subsequent production of red ferric sulphocyanide. 

4. Schonbein’s Test.—It has been stated that a very delicate means 
of detecting HCy is based upon its action on filtering paper, 
soaked, first in a 3 per cent. alcoholic solution of guaiacum 
resin, and then in a 2 per cent. solution of cupric sulphate, 
and exposed to the air. The presence of HCy causes the pro- 
duction of a blue color. The paper may be either moistened 
with the suspected solution or exposed to its vapour. 


Cyanides are known (practise upon solution of potassium cyanide—KCy)— 


1. By effervescing and giving off the odor of hydrocyanic acid when 
heated with sulphuric acid. 


2. By answering to all the tests for hydrocyanic acid above mentioned. 


4Vote.—In using the silver test to a soluble cyanide, the reagent must be added 
in excess, as argentic cyanide is soluble in alkaline cyanides to form double 


CYANIC ACID AND FERROCYVANIDES. Al 








cyanides of silver and the alkali used. Excess of argentic nitrate, however, 
decomposes these compounds, and forms insoluble argentic cyanide. The 
previous addition of a s/igh¢ excess of dilute nitric acid ensures the immediate 
separation of the argentic cyanide, by preventing the reaction just referred to. 

3. Insoluble cyanides yield cyanogen when heated fer se in a small 
dry test-tube, the open end of which has been drawn out into 
a jet after the introduction of the cyanide. The application of 
a light to the jet causes the characteristic flame of cyanogen. 


95. CYANIC ACID and CYANATES, CYANURIC ACID and 
FULMINIC ACID. 


Cyanic Acid—HCyO—is characterised— 

1. By being a colorless liquid, having a strong pungent odor, greatly resembling 
acetic acid, or sulphurous acid when in small quantity, and forming ammonium 
bicarbonate on adding water. 

2. By changing into a white solid zsomer on keeping, heat being evolved, but no 
decomposition occurring. 

Cyanates are known— 

1. By giving, when moistened, a bicarbonate. (The potassium salt—KCyO—for 
instance, forms potassium bicarbonate—K HCO.) 

2. By producing urea when evaporated with an ammonium salt. 


Cyanuric Acid is a polymeric modification of cyanic acid, which is recognised— 
1. By being a crystalline solid, yielding cyanic acid on applying heat. 
2, By not being decomposed by strong hot HNO; or H,sO,. 
Fulminic Acid (intermediate between the two above acids) differs from both by the fearful 
explosibility of its salts. 


96. THIOCYANATES (Sulphocyanates). 
(Practise upon solution of potassium sulphocyanate—K Cys). 


Sulphocyanates are recognised— 

1. By being usually colorless and soluble, and evolving hydrocyanic 
acid and depositing sulphur on heating with sulphuric acid. 

2. By producing with Fe,Cl,, or any ferric salt, a blood-red solution 
of ferric sulphocyanate—Fe,(CyS),—the color of which is not 
destroyed by HCl, but disappears on adding mercuric 
chloride—HgCl,. 


27. FERROCYANIDES. 
(Practise upon solution of potassium ferrocyanide—K,FeCyg). 


Ferrocyanides are mostly insoluble in water, except those of the metals of the 
first and second groups. They are characterised— 

1. By giving off hydrocyanic acid and forming a deposit on heating 
with sulphuric acid. a 

2. By giving with FeSO, or any ferrous salt a white precipitate 
of potassium ferrous ferrocyanide—K,Fe(FeCy,)—changing 
quickly to blue. att 

3. By yielding with Fe,Cl, or any ferric salt a dark blue precipitate 
of ferric ferrocyanide—(Fes)9(FeCy¢)3—insoluble in HCl, but 
turned reddish-brown by KHO, which decomposes it into 
ferric hydrate and potassium ferrocyanide. The original blue 
is restored by adding HCl. 

4. Cupric salts produce a reddish-brown precipitate of cupric ferro- 
cyanide—Cu,FeCy,—insoluble in acids, dissolved by NH4HO, 
but left unaltered on evaporating off the ammonia. 

s, By precipitating a white ferrocyanide from a solution of a lead salt. 

6. By yielding a white mercuric ferrocyanide in a mercuric solution. 


42 DETECTION, ETC., OF ACIDULOUS RADICALS. 





7. By giving no effect with magnesium salts but a white gelatinous - 
precipitate on the addition of a solution containing a zinc salt, 
soluble in NH,HO. 

8. By producing with argentic nitrate—AgNO,—white gelatinous silver 
ferrocyanide, dissolved by NH,HO. 


None of these precipitates can be produced in alkaline solutions ; and they form 
best in slightly acid solutions. 


28. FERRICYANIDES. 

(Practise upon solution of potassium ferricyanide—K,Fe,Cy,».) 

Most ferricyanides are insoluble, those of the alkalies and of the barium 
group being exceptions. They are recognised— 

1. By yielding an odor of hydrocyanic acid, and a deposit on heating 
with sulphuric acid. 

2. By producing with FeSO, or any ferrous salt dark-tinted Zurnbull’s 
blue—¥e,Fe,Cy,.—insoluble in acids, but forming K,Fe,Cy» 
when boiled with KHO, and depositing dirty green Fe(HO).,. 

3. By producing a brownish coloration when added to Fe,Cl, or any 
ferric salt in solution, from which H,SO;, SnCl,, and other 
reducing agents throw down Zurndbull’s blue or Prussian blue 
(distinction between HFe,Cy,. and H,FeCy,). 

4. By giving no precipitate in a lead solution (another distinction of a 
Serricyanide from a ferrocyanide). 

5. By throwing down mercurous ferricyanide of a brownish red colour 
from a mercurous solution. 

6. By yielding with argentic nitrate solution an orange precipitate of 

argentic ferricyanide. 
- Mercuric salts, giving no precipitate. 
. Stannous salts, a white precipitate, soluble in HCl. 
g. Stannic salts, no visible alteration. 


29. HYPOPHOSPHITES. 

(Practise upon solution of calcium hypophosphite—Ca(PH,0O,)..) 

The silver salt alone is insoluble in water, and few are insoluble in alcohol. 
The following reactions serve for their detection :-— 

1. When heated in a solid state, they take fire, evolving phosphuretted 
hydrogen, and leaving a residue of pyrophosphate. 

Note.—This must be done on porcelain, as they destroy platinum foil. 

2. With argentic nitrate they give a white precipitate, which turns 
brown owing to its reduction to metallic silver. 

3- With mercuric chloride they yield, when slightly acidulated with 
HCl, a precipitate of calomel, which, on heating, turns dark, 
Owing to a reduction to the metallic state. 

4. After removal of the base, the free hypophosphorous acid, when 
boiled with solution of cupric sulphate, will give a deposit of 
metallic copper. 

5. Treated with ammonium molybdate—(NH,),MoO,—they give a 
fine d/we precipitate. As afterwards mentioned, phosphates give 
a yellow, and consequently when the solution contains both 
classes of salts the precipitate is green. This forms an excellent 
and rapid method of checking any commercial sample of 
hypophosphites. 

They are distinguished from phosphites by not giving precipitates with 
neutral barium, or calcium, chloride, or with plumbic acetate. In performing 


com 


_ PHOSPHOROUS ACID AND ORTHOPHOSPHATES. 43 








the 4th reaction, the base, if calcium, is removed by oxalic acid, if barium, by 
sulphuric acid, and if a heavy metal, by sulphuretted hydrogen. 


30. PHOSPHOROUS ACID—H,P0,—and PHOSPHITES 


are distinguished as follows :— 

1. Heated on platinum foil, they burn. They are powerful reducing agents. 

2. The only phosphites soluble in water are those of K, Na, and NH,, but acetic 

acid dissolves all, except plumbic phosphite. 

3. With zinc and sulphuric acid (nascent hydrogen) they yield phosphuretted hydro- 
gen, burning with an emerald-green colour, and throwing down Ag;P, as well 
as Ag from AgNO, in solution. 

. They give precipitates with neutral barium, and calcium chlorides, and also with 
plumbic acetate, which hypophosphites do not. 

. Heated with mercuric chloride or argentic nitrate, they yield a precipitate of 
metallic mercury or silver. 


mn - 


31. META- AND PYRO-PHOSPHORIC ACIDS AND THEIR SALTS. 


Metaphosphoric Acid—HPO,—is a glassy solid, not volatile by heat. _It is freely soluble in 
cold water, and is converted by boiling into orthophosphoric acid. It is known by giving 
a white precipitate with argent-ammonium nitrate, and by its power of coagulating albumen. 


Metaphosphates are known by— 
1. Giving no precipitate with ammonium chloride, ammonium hydrate, and mag- 
nesium sulphate, added successively. 
2. By giving a white precipitate of argentic metaphosphate —AgPO,—with argentic 
nitrate only in neutral solutions, and soluble both in nitric acid and ammonium 
hydrate. 


Pyrophosphoric Acid—H,P,0,—is also soluble in water and convertible by boiling into 
orthophosphoric acid. It gives a white precipitate with argent-ammonium nitrate, but 
does not coagulate albumen. Pyrophosphates are insoluble in water, except those of the 
alkalies. Their tests are not very well defined, but they give— 

1. A white precipitate of argentic pyrophosphate—Ag,P,O,;—with argentic nitrate in 
a neutral solution only, and soluble both in nitric acid and ammonium hydrate. 
2. (NH,),Mo0, does not produce an immediate precipitate. 


32. ORTHOPHOSPHORIC ACID and ORTHOPHOSPHATES. 


Orthophosphoric acid—H;PO,—is a liquid with a strongly acid reaction, 
converted by heat first into pyro- and finally into meta-phosphoric acid, 
which remains as a glassy residue. It is— 

1. Not volatile by a red heat. 

2. It gives a yellow precipitate of argentic phosphate—Ag3PO,—when 
treated with argent-ammonium nitrate, soluble both in nitric 
acid and ammonium hydrate. 


Phosphates are as a rule insoluble in water, except the alkaline ones. They 
are readily soluble in dilute acids, and entirely reprecipitated on neutral- 
ising by an alkali or alkaline carbonate. Calcium, strontium, and barium 
phosphates are only partly soluble in dilute sulphuric acid, being converted 
into a soluble phosphate and an insoluble sulphate of the metal. If the 
insoluble sulphate be filtered out, the addition of an alkali causes only a 
slight precipitate of a dimetallic phosphate, and a phosphate of the alkali 
used is left in solution ; but it is only after the use of sulphuric acid that 
any phosphate thus remains dissolved. 


Phosphates are detected as follows (practise on solution of disodium-phos- 
phate—Na, HPO, :— 
1. With barium or calcium chloride white precipitates are produced, 


44 DETECTION, ETC., OF ACIDULOUS RADICALS. 


ee EEE eee 


soluble in acetic acid (distinction from oxalates) and all stronger 
acids. 

2. With argentic nitrate a lemon-yellow precipitate of argentic phos- 

phate forms, soluble both in nitric acid and ammonium hydrate. 

3. With ferric chloride in the presence of ammonium acetate a white 

precipitate of ferric phosphate appears, insoluble in acetic acid. 

4. With magnesia mixture phosphates yield a white crystalline pre- 
cipitate, forming slowly in dilute solutions, consisting of ammo- 
nium-magnesium phosphate—Mg(NH,)PO, + 6H,O—soluble 
in acetic and all acids. 

- With solution of ammonium molybdate in nitrie acid a yellow 
precipitate is produced, insoluble in nitric acid, but soluble in 
ammonium hydrate. | 

6. With uranic nitrate—UrO,(NOs;)2—phosphates yield a yellow 
precipitate of uranic phosphate, also insoluble in acetic acid. 

7. With mercurous and bismuthous nitrates white precipitates are 
formed, the former soluble and the latter insoluble in nitric 
acid. 

- 8. With any soluble salt of lead a white precipitate of plumbic phos- 

phate is produced, soluble in nitric acid, but insoluble in acetic 
acid or ammonium hydrate. 


NotEe.—Magnesia mixture is made by dissolving ordinary magnesium 
carbonate in a slight excess of dilute HCl, then adding to this solution 3 
of its bulk of strong NH4HO, and finally stirring in solid NH,Cl until the 
precipitate is dissolved. 


OL 


33. ARSENIOUS ACID and ARSENITES. 


Arsenious Acid—H;AsO3—is not known in the free state ; but its anhydride 
—As,O;—is commonly sold as arsenious acid, and when— 


1. Dropped upon red-hot charcoal or coal, or heated in a dry tube 
with black flux (or a mixture of dry sodium carbonate and 
potassium cyanide), the metalloid As, is set free, and volatilises 
with a garlic odor, producing a steel-grey mirror on the sides 
of the tube. 

2. Dissolved in water only, and argent-ammonium nitrate added, a 
canary-yellow precipitate of argentic arsenite—Ag;AsO3;—is 
produced, soluble in excess of either NH4HO or HNO3. 

3- A pure aqueous solution, mixed with cupr-ammonium sulphate, 
gives a bright-green cupric arsenite—Scheele’s green—CuHAsO3 
—also soluble in NH,HO or in HNOs. 

4. Any solution yields all the tests for arsenic (see page 1 ee 


Arsenites behave peculiarly in many respects. Ammonium arsenite leaves 
arsenious acid on evaporating a solution, while potassium and sodium 
arsenites possess a degree of alkalinity which no excess of arsenious acid 


will disturb. Ba, Sr, and Ca form soluble hydrogen salts. All other 
arsenites are insoluble. 


Neutral solutions of arsenites are possessed of the undermentioned distinctive 
peculiarities :— 
1. CuSO, throws down greenish cupric arsenite. 
2. AgNO; is transformed into yellow insoluble argentic arsenite. 
3- HS, 2x the presence of hydrochloric acid, gives a yellow precipitate 
of arsenious sulphide. 
4 The solution gives the usual tests for arsenic (see page 1 5). 


ARSENIC ACID AND CHROMATES. 45 


SS RS Ee 


34. ARSENIC ACID and ARSENIATES. 


Arsenic Acid—H;AsO,—is known by the following characters :— | 
1. The crystals are deliquescent, white, and strongly acid. Heated, 
they leave a residue, which, on moistening with water, is also 
acid. 
2. It is strongly corrosive and blisters the skin. It gives brick-red 
Ag;AsO, on adding argent-ammonium nitrate. 


Arseniates behave in every respect exactly like phosphates, except that they 
give a brick-red precipitate with argentic nitrate, instead of a yellow. 
Insoluble arseniates are best treated by boiling: with NaHO, filtering, 
exactly neutralising the filtrate with dilute HNO, and then getting the 
brick-red precipitate with AgNO. 


30. MANGANATES. 
Manganates are unstable compounds, and only the alkaline salts dissolve in water, forming 
. green solutions, 


I. Soluble manganates decompose spontaneously, depositing MnO,, the green color 


changing to purple or reddish violet, owing to the formation of a perman- 
ganate. 


3K,Mn0O, + 2H,O =2K MnO, + 4KHO + MnO, 
2. Dilute acids effect this change more rapidly, and the reaction is very delicate. 


The free hydrate is then replaced by a chloride, nitrate, or sulphate. 
3. Strong, heated H,SO, acts as represented in this equation :— 


K,Mn0O, =f 2H,SO, sand K,SO, GP MnSO, ae 2H,O ar O.. 


4. Strong HCl causes the evolution of Cl, The other actions are similar to those 
of permanganates, but less energetic. 


36. PERMANGANATES. 


(Practise on solution of potassium permanganate—K MnQ,.) 
Permanganates are known— 


1. By the violet color of their solutions, which is entirely bleached by 
oxalic acid or by heating with hydrochloric acid and dropping 
in rectified spirit. 

2K MnO, + 5 H2C204 + debe ey K2SO4 + 2MnSO, + toCO, + 8H,O. 

2. By giving off oxygen on heating. 

3. By giving off oxygen when heated with sulphuric acid, often with 
explosive violence. 

4. By evolving chlorine when simply mixed with hydrochloric acid. 


37. CHROMIC ACID and CHROMATES. 


Chromic Acid—H,CrO,—not being capable of isolation, is represented by 
its anhydride—CrO;. This is a dark red crystalline solid, giving off oxygen 
when heated, and when mixed with an aqueous solution of hydrogen peroxide 
—H,O,—a deep blue liquid results, which is believed to contain perchromic 
act@—HCrO, or H,Cr,0,. The liquid decomposes rapidly, unless ether be 
added, which lengthens its existence. 

_ This test, for either CrO; or H,O,, is exceedingly delicate, the ethereal 
solution of perchromic acid separating from the water and thus concentrating 
the color into a small bulk of ether. 


Chromates of the alkalies are soluble, while those of the other metals are 
chiefly insoluble, but have very brilliant colours. They are very poisonous 


46 DETECTION, ETC., OF ACIDULOUS RADICALS. 


ec a 


and are detected as follows (practise on solution of K,CrO, and K,Cr,0O, 
respectively) :— i 


1. Soluble chromates give a yellow precipitate with plumbic acetate 
or barium chloride, soluble in nitric acid, insoluble in acetic 
acid. The lead salt is darkened in color by alkalies, and 
dissolves by free excess of hot KHO. 

. With argentic nitrate a dark red precipitate, also soluble in nitric 

acid, and in NH,HO, but not in acetic acid. 

Boiled with hydrochloric acid and alcohol, or any reducing agent 
(for instance, sulphurous acid), they turn green, owing to the 
production of chromic chloride (or sulphate). 

4. Treated with sulphuretted hydrogen, in the presence of hydrochloric 

acid, they turn green, and a deposit of sulphur takes place :-— 


2K,Cr,0, + 16HCl + 6H,S = 2Cr,Cl, + 4KCl + 3S. + 14H,0. 


s. Soluble chromates treated with an acid turn orange; and soluble 
dichromates, when treated with potassium hydrate, turn yellow. 
In this way they are mutually distinguished. 
. Heated with strong H,SO, they give off oxygen. 
Treated with an excess of sulphuric acid, and shaken up with 
ozonised ether (solution of hydric peroxide in ether), they give 
a gorgeous blue with the most minute traces. 


N 


wm 


ot GN 


38. STANNIC ACID and STANNATES (Stannites ?). 


This is an unimportant compound, and is thrown down by an alkaline hydrate from a 
stannic salt. It is sometimes stated to be endowed with the composition Sn(HO),, and at 
others, SnO(HO), (H,SnOs). 

Stannates are formed by the solution of the acid in an alkaline hydrate, and are detected 
in the examination for metals. 

Stannites are said to be formed by the solution of stannous hydrates in an alkaline 
hydrate. They decompose on boiling with KHO, forming stammates and throwing down 
metallic tin. 


39. ANTIMONIC ACID. 


This is the white precipitate having the composition HSbO,, formed on adding strong HCl 
to potassium antimoniate ; and it is detected in the examination for metals. 


40. FORMIC ACID and FORMATES. 


Formic Acid—HCHO,—is the “ organic” acid which contains the highest 
percentage of oxygen, and approaches most nearly in composition to the 
suppositious carbonic acid——H,CO;. It is a tolerably stable liquid, boiling at 
the same temperature as water. Formates are all soluble in water, and behave 
as follows :— : 

1. Heated to redness they decompose without blackening. 

2. Heated with H,SO, they evolve CO, which, being free from CO,, 
gives no effect when passed through “me-qwater, but burns with 
the usual pale blue flame. The reaction is :— 

HCHO, = COFPRE.@- 


3. Readily reduce argentic nitrate, when boiled, metallic silver 
separating. 


ACETATES—VALERIANATES—SULPHOVINATES. 47 
a NE na 
41. ACETIC ACID and ACETATES. 


(Practise on sodium acetate—-NaC,H,0,). 


This acid is characterised by its odor of vinegar. The strong acid chars 
when heated with strong H,SO,. 

Acetates are without exception soluble in water (AgC,H;0, and HgC,H,0, 
are sparingly dissolved). They are decomposed by a red heat, yielding 
acetone if the heat rise gently and the mass be not alkaline, and leaving a 
carbonate, oxide, or metal, according to the nature of the basylous radical. 
When heated with alkalies marsh gas—CH,—is evolved. The reaction is of 
this type :— 

NaC,H,0, + NaHO = Na,CO, + CH, 

In the case of no hydrate or carbonate being present, the following is an 

example of the effect of heat on acetates :— 


Ba(C,H;0,), = BaCO; + C,H O (Acetone). 


Acetates of easily reducible metals, such as copper, yield, when heated, a 
distillate of acetic acid, leaving a residue of the metal, or in some cases of 
oxide. The presence of acetates is analytically determined as follows :— 

1. By evolving an odor of acetic acid when heated with sulphuric acid. 

2. By a characteristic apple-like odor of “acetic ether”—C,H;(C,H.O,) 
—which they evolve when heated with sulphuric acid and 
alcohol. 

3. By the deep red color which they produce with neutral ferric 
chloride—ferric acetate, Fe(C,H;0,),—daischargeable by both 
hydrochloric acid and mercuric chloride. 


42. VALERIANIC ACID and VALERIANATES. 


Valerianic Acid —HC,H,O,—is a liquid, which is— 
Volatile, malodorous, colorless, and oily. It reddens test-paper, and 
dissolves in most menstrua. 


The general characters of Valerianates are :— 

I. A more or less strong odor of valerian root when warmed. or 
moistened. 

2. They give, when heated with sulphuric acid, an odor of valerian 
and a distillate which, on the addition of solution of cupric 
acetate, forms, after the lapse of some time, an oily precipitate ; 
gradually solidifying, by the absorption of water, into a greenish- 
blue crystalline solid. 


43. SULPHOVINATES (Ethyl sulphates). 


_ These salts, derived from ethyl hydrogen sulphate—C,H;HSO,—behave 

as follows :— 
1. Heated with strong sulphuric acid, they evolve a faint ethereal odor. 
2. They give no precipitate in the cold with barium chloride; but on 
boiling, a white precipitate of barium sulphate falls, and a smell 
of alcohol is perceived. The addition of a little solution of 
barium hydrate after the chloride and before boiling, facilitates 
the reaction ; but in this case all metals precipitable by a fixed 

alkali must first, of course, be removed. 

3- Heated to redness, they leave a sulphate of the metal. 
4. Heated with sulphuric acid and an acetate, or with strong acetic 
acid, they evolve acetic ether with its characteristic apple odor. 


48 DETECTION, ETC., OF ACIDULOUS RADICALS. 


a 


44. STEARIC ACID—HC,,H,,0,—and STEARATES. 


This acid is usually so distinguished by its appearance and behaviour on 
peing heated that further tests are useless. The characters are :— 

1. A white, odorless, fatty solid, melting by heat and soluble in 
absolute alcohol, the solution having an acid reaction. 

2. Giving, when dissolved in KHO and the solution as nearly neutral- 
ised as possible, a white insoluble precipitate of plumbic stearate 
—Pb(C,,H;,0,),—on the addition of plumbic acetate, which is 
insoluble in ether (distinction from plumbic oleate). 


Stearates of the alkalies are alone soluble in water. 

Any stearate heated with dilute HCl gives the free acid, which floats 
as an oily liquid, solidifying on cooling to a white mass. This 
test is applicable to the analysis of soap (4ard, containing Na, 
or soft, in which K is present). 


45. OLEIC ACID and OLEATES. 


Oleic Acid—HC,,H,,0,—is usually an oily liquid, but remains solid below 
59° Fahr. when crystallised from alcohol. 
It does not dissolve in water, but is taken up by ether and by strong 
alcohol, the latter solution being acid in reaction. 


Oleates of K and Na alone dissolve in water. Acid oleates are all liquid and 
soluble in cold absolute alcohol and ether. 
1. They do not separate out from either of these solvents when a hot 
solution is cooled (distinction from stearates and palmitates). 
2. Plumbic oleate is precipitable like plumbic stearate, but is separated 
and distinguished from it by dissolving in ether. 


46. LACTIC ACID—HC,H,0,—and LACTATES. 


The pure strong acid resembles g/ycerine in appearance, liberates hydrogen 
on adding zinc, and on heating takes fire and burns away with a pale flame, 
gradually becoming luminous. It dissolves in ether. It gives pure CO when 
heated with sulphuric acid. Boiled with solution of potassium permanganate 
it gives the odour of aldehyd. | , 


Lactates are not very soluble in water. They— 
1. Are insoluble in ether. 
2. Argentic lactate—AgC;H;O,;—when boiled gives a dark precipitate, 
which on subsidence leaves a blue liquid. 
3. Strong solution of an alkaline lactate, when boiled with HgNO,, 
deposits crimson or pink mercurous lactate—HgC,H;O3. 


47. OXALIC ACID and OXALATES. 


(Practise on oxalic acid—H,C,O,—and on “salts of sorrel ”— 
‘ KHC,0,H.C,0720,07; 


The acid is very common, and is recognised— 

1. By its colourless prismatic crystals, which are strongly acid, effloresce 
when exposed to dry air, and volatilise on heating with partial 
decomposition. 

2. By the complete discharge it effects of the color of a solution of 
potassium permanganate acidulated with dilute H2SO,. 


SUCCINATES—MALATES—TARTRATES. 49 





3. By producing free H,SO, when added to solution of CuSO,. (This 
is one of the very rare instances in which SQ, is replaced by 
another acid radical and H,SO, liberated.) 

4. By giving the reactions of an oxalate. 


Oxalates of the alkalies are soluble, the others insoluble, in water. Insoluble 
oxalates dissolve in hydrochloric but not in acetic acid. They are known by— 
1. Not charring when heated, but only turning faintly grey ; followed 
by a sudden glow of incandescence, which runs through the 

mass. 

2. Not charring when heated with sulphuric acid, but yielding CO and 
CO, with effervescence. 

3. Not effervescing with cold dilute sulphuric acid; but at once 
liberating CO, with effervescence on the addition of a pinch 
of manganese peroxide. 

4. With calcium chloride or barium chloride in a neutral or alkaline 
solution, they give a white precipitate of calcium or barium 
oxalate, zmsoluble in acetic acid, but soluble in hydrochloric acd. 

(For separation of oxalates from tartrates, etc., see No. 78.) 


48. SUCCINIC ACID—H,C,H,0,—and SUCCINATES. 


This acid is a white crystalline solid. It is known— 
1. By not charring with strong hot sulphuric acid. 
2. By subliming in a tube open at both ends, in silky needles, wethout giving off an 
irritating vapor (distinction from benzoic acid). 
3. By burning, when heated on platinum, with a blue smokeless flame. 


Succinates are recognised as follows :— 

1. With pers chloride, a brownish-red precipitate of ferric succinate—Fe,(C,H,O,)s 
—is formed. 

2. With hydrochloric and sulphuric acids no precipitate is produced (d¢stinction from 
benzoates). With glumbic acetate, a white precipitate of p/umbic succenate, 
soluble in succinic acid, succinates, and plumbic acetate. 

3. Barium succinate is soluble in hydrochloric acid, hence no effect results from the 
addition of succinic acid to barium chloride ; but alcohol and ammonium 
hydrate give rise to a white precipitate (another point of distinction Jrom 
benzoates). 


49. MALIC ACID and MALATES. 


Malic Acid—H,C,H,O,—is a colorless, crystalline, very deliquescent acid, freely soluble 
in water and alcohol. Acid malates are most stable. The characters are :— 

1. Calcium chloride, added to a neutral solution of a malate, gives no precipitate. 
Alcohol, however, even if added in small quantity, throws down a white 
precipitate ; and boiling aids the effect. 

2. Strong H,SO, gives no charring for some time (a ¢artrate is carbonised in a few 
minutes). 

3. Amorphous f/umbic malate fuses below 100° C. in water, but not in an air-bath. 


50. TARTARIC ACID and TARTRATES. 
(Practise upon the free acid and also upon “ Rochelle salt.”) 


Tartaric Acid—H,C,H,O,—is a strong acid, soluble in water and spirit. 

1. It forms usually oblique rhombic prismatic crystals, of an acid taste. 

2. It is decomposed by heat, giving off the odor of burnt sugar, and 
leaving carbon. A similar effect is produced by warming with 
strong H,SO,, which blackens and carbonises it in a few minutes. 

3. With potassium acetate—KC,H,0,—it produces a white crystalline 
precipitate of Aotassium hydrogen tartrate — KHC,H,O,— in 
either an aqueous or an alcoholic solution, soluble in much 
water, but not in spirit. Stirring or violent shaking promotes 
the formation of the salt. 


\ 


4 


50 DETECTION, ETC., OF ACIDULOUS RADICALS. 


The same compound is produced on adding any potassium salt, provided 
the liquid contain excess of free tartaric acid only. 


Tartrates of the alkalies are mostly soluble ; but the others are insoluble. 
The hydrogen tartrates of K and (NHg) are nearly insoluble. Tartrates are 
recognised by the following characters :— 

1. Heated to dull redness they char rapidly and give off a smell of 
burnt sugar. The black residue contains the metal as car- 
bonate if it be K, Na, Li, Ba, Sr, or Ca; but the tartrates of 
other metals usually leave the oxides, or more rarely (as in the 
case of Ag,C4H,O,) the metal. 

2. Heated with strong sulphuric acid, they blacken rapidly, and give 
first a smell of burnt sugar, and afterwards evolve SO». 

3. Neutral solutions (free from more than a trace of ammonium salts) 
give, on adding calcium chloride, a white precipitate of calaum 
tartrate, which, when freed from other salts by washing, dissolves 
readily in cold solution of potassium hydrate, but is again pre- 
cipitated on boiling. The precipitate is somewhat soluble in 
NH,Cl, but not in NH,HO. 

4. Mix a tartrate with sodium carbonate, and filter the slightly alkaline 
solution, so that the only metal present shall be sodium. If 
this clear solution, after sgt acidulation with acetic acid, be 
mixed with argentic nitrate, the whole, on heating nearly to 
boiling in a clean tube, deposits a beautiful mirror of metallic 
silver upon the test-tube employed. 

5. Atartrate prevents the precipitation (more or less perfectly) of the 
salts of Pb, Bi, Cd, Cu, Pt, Fe,, Mn, Ni, Co, Cr, and Zn, by an 
alkaline hydrate in excess, or a phosphate. 


51. CITRIC ACID and CITRATES. 
(Practise upon the free acid and upon potassium citrate.) 


Citric Acid—H,C,H,O;—is soluble in water and alcohol, but insoluble in 
pure ether. It entirely burns away when heated to redness in the air ; 
blackens slowly when heated with strong sulphuric acid; and when neutral- 
ised by ammonium hydrate, and the solution cooled, the solution gives 
no precipitate with calcium chloride until it has been boiled. Added to 
ferric, chromic, or aluminic salts in solution, it prevents their precipitation 
by ammonium hydrate. 


Citrates exhibit the following characters :— 

1. Heated alone, they char slowly, and evolve an odor of burnt sugar, 
but not so intense as that of a tartrate. Ata dull red heat, the 
citrates of K, Na, Li, Ba, Sr, and Ca leave their carbonates ; 
but those of most other metals leave the oxides. Argentic 
citrate leaves the metal. : 

2. Heated with strong sulphuric acid, they slowly blacken, and evolve 
a slight odor of burnt sugar. wan 

3. Mixed in the cold with calcium chloride, in the presence of a slight 
excess of ammonium hydrate, they give no precipitate ; but on 
boiling, calcium  citrate—Ca,(C;H;O;),—separates as a white 
precipitate. If this precipitate be filtered hot, and washed with 
a little boiling water, it is found to be quite insoluble in cold 
solution of potassium hydrate, but readily soluble in neutral 
solution of cupric chloride. 

4. Mixed with argentic nitrate and boiled, no mirror of metallic Hie 

is produced. 





MECONATES—CARBOLATES—BENZOATES. 51 











52. MECONIC ACID and MECONATES. 

Meconic Acid—H,C,H,0,3H,O—is a white powder, with a strongly acid 
reaction, soluble in water, alcohol, and ether, and giving the reaction for 
meconates. 

Meconates communicate a red color to ferric chloride solution. This color 
is not discharged by HgCl, nor by dilute HC?. By this means it is distin- 
guished from a su/phocyanate and an acetate. 


53. CARBOLIC ACID (or Phenol)—C,H,HO)—and CARBOLATES (Phenates). 


The qualities of this body are very distinctive. 

1. It is a colorless, crystalline solid, melting at not lower than or‘s° F. 
(33° C.), and not volatile at 212°, having the odor and taste of 
creasote, being very poisonous, and not reddening test-paper. 

2. The crystals deliquesce readily, forming a liquid which does not 
mix freely with water, but incorporates readily with alcohol, 
ether, and glycerine. 

3. Mixed with HCl and exposed to the air on a strip of deal, it 
becomes greenish blue. 

4. It coagulates albumen. It does not rotate polarised light. 

5. Saturated with ammonia gas—NH,—and heated in a closed tube, 
aniline is formed :— 

C;,H;HO + NH; = C,H;H,.N + H,O. 

6. It does not decompose carbonates. 

- NH,HO and CaOCl, or Na,OCl,, produce a blue liquid. 

. It unites directly with strong H,SO, to form sulpho-phenic (or 

sulpho-carbolic) acid—C,H;HSQ,. 

g- With bromine water it gives a white precipitate of tribromophenol 
—C,H,Br,0. 

Carbolates give the following reactions :— 

1. When heated alone, they evolve the odor of carbolic acid and 
decompose. 

2. Heated with strong sulphuric acid, they also smell of carbolic acid. 

3. Ferric chloride causes a reddish-violet color. 

Sulpho-Carbolates behave similarly, but, after fusion with KNO3 and redis- 
solving the residue in diluted HCl, they also give the reactions of a sulphate 
with barium chloride. 

04. BENZOIC ACID and BENZOATES. 

Benzoic Acid —HC,H,O,—is of characteristic appearance, being usually 
seen in light, feathery, flexible, nearly colorless crystalline plates or needles, 
and containing a trace of an agreeable volatile oil, unless it is the artificial 
acid prepared from naphthalene, when it is odorless. 

1. It is only slightly soluble in water, but dissolves in three parts of 
alcohol, and in solutions of soluble hydrates. 

2. Heated in the air, it burns with a luminous smoky flame; and 
when made hot in a tube open at both ends, sublimes in 
needles, giving off an zrritating vapor. 

Benzoates possess the following general qualities :— 

1. Heated with'sulphuric acid they evolve the odor of benzoic acid, 
and darken. | 

2. Ferric chloride, in a solution made sizghtly alkaline by ammonium 
hydrate, gives a reddish-white precipitate—ferric benzoate— 
Fe(C,;H;O,),—soluble in acids (derzoic included). If this pre- 
cipitate be now filtered out and digested in ammonium hydrate, 
it is decomposed into a precipitate of ferric hydrate, and a 


onl 


e 


52 DETECTION, ETC., OF ACIDULOUS RADICALS. 





solution of ammonium benzoate, which is separated by filtration 
and treated as in 3. 

3. Strong hot solutions of benzoates yield crystals of benzoic acid when 
hydrochloric acid is added and the solution allowed to cool. 


55. SALICYLIC ACID (HC,H,0,). 


This acid occurs in prisms, when crystallised from a solution in alcohol in 
which it is readily soluble. It is freely dissolved by hot water, but not 
= readily by cold, requiring 1,800 parts of the latter to completely dissolve it. 
1. Its aqueous solution gives with Fe,Cl, a deep violet coloration. ‘The 
compounds with methyl, ethyl, etc., give this reaction, as well 
as the ordinary salts. 

2. Its methyl salt, formed by warming a salicylate with sulphuric acid 

and wood spirit, has a very fragrant odor. 

From most other solid bodies it may be separated by taking advantage of 
its exceptionally great solubility in ether. In the event of its presence in 
an organic liquid (such as milk) it or its salts may be procured in a pure 
condition by dialysis. 


56. TANNIC, GALLIC, and PYROGALLIC ACIDS. 


Tannic Acid—C,,H,,O,,—is soluble in water and alcohol, and very soluble 
in glycerine. It is insoluble in pure dry ether, but dissolves readily in 
ether containing a little water. 

Gallic Acid —H,C,H,0;H,O—is slightly soluble in cold water, but readily in 
boiling ; it is also freely soluble in glycerine, and slightly in alcohol 
and ether. 

Pyrogallic Acid—C,H,O,—is very soluble in water, the solution rapidly 
absorbing oxygen from the air and becoming brown. It also dissolves 
in alcohol and ether. | 


DISTINCTION BETWEEN GALLIC, TANNIC, AND PyROGALLIC ACIDs. 


BEHAVIOUR OF THE 


ote panbaies GALLIC. TANNIC. PYROGALLIC. 

Ferrous salts— A dark solution | The same effect | A blue solution. 
FeSQ,. is formed, as Gallic. 

gradually de- 
positing a 
precipitate. . 

Ferric salts— Purplish pre- | Same as pre- | A red solution. 
Pecit cipitate im- ceding. 

mediately 
formed. 

Calcium hydrate | A brownish pre- | A white preci- | Instantaneous 
—CazHO—in cipitate, be- pitate slowly production of 
the form of coming deep changing. a purple solu- 
Milk of Lime. brown in a tion becoming 

few seconds. brown by oxi- 
dation. 

Gelatine . . .| No _ precipitate | Immediate No precipitate. 

(except in the brownish 
presence of precipitate. 


gum). 


CHLORIDES—BROMIDES—IODIDES. 53 


57. SEPARATION OF CHLORATES AND CHLORIDES. 


Note.—The tests which follow are applicable to tests for adulterations, where, for obvious 
reasons, the confirmatory test for a suspected adulterant would not apply. 


(Practise on mixed solutions of KCl and KCI1Q3.) 


_ Add excess of argentic nitrate, filter out the argentic chloride formed, and 
then acidulate with sulphuric acid, and drop in a fragment of zinc, when, if a 
chlorate be present, a second precipitate of argentic chloride will form. 


58. DETECTION OF CHLORIDES IN THE PRESENCE OF BROMIDES. 
(To be practised on a mixture of KCl and KBr.) 


The solution is divided into two parts, in one of which the bromide is 
proved by the addition of chlorine water, and shaking up with chloroform. 
The second portion is either (1) Evaporated to dryness, the residue placed 
in a tube retort with a little potassium dichromate and sulphuric acid, while 
into the receiver is placed a little dilute ammonium hydrate, and distillation is 
proceeded with, when, if a chloride be present, the liquid in the receiver will 
be colored yellow; or (2) Precipitated with excess of AgNO;, washed on 
a filter, percolated with dilute NH,HO (1 in 20) and nitric acid added to the 
percolate, when a distinctly curdy white precipitate proves the presence of 
chlorides. This latter method is simple, and rarely fails if, on adding the 
acid, a mere cloud be disregarded. 


59. DETECTION OF BROMIDES IN THE PRESENCE OF IODIDES. 
(Practise on a mixture of KBr and KI.) 


Add to the solution a very small quantity of starch paste and then a drop 
or two of chlorine water, when a blue color will be produced, proving the 
iodide. Continue to add more chlorine water until this blue is entirely dis- 
charged, and then shake up with chloroform, when, if a bromide be present, 
the characteristic golden color will be communicated to the chloroform. 


60. DETECTION OF CHLORIDES IN THE PRESENCE OF IODIDES. 
(Practise on a mixture of KCl and KI.) 


Add excess of argentic nitrate, warm, pour off the supernatant liquid, wash 
with warm water, and shake up the precipitate in dilute solution of ammonium 
hydrate (1 in 3). The argentic iodide will remain insoluble, while the chloride 
will dissolve and may be detected in the solution, after filtration, by reprecipita- 
tion with excess of nitric acid. As argentic iodide is not absolutely insoluble 
in ammonium hydrate, a mere cloud on adding the nitric acid is to be dis- 
regarded. ‘This test is only accurate in the insured absence of a bromide, 
proved as above directed (see 59). 


61. SEPARATION OF AN IODIDE FROM A BROMIDE AND CHLORIDE. 
(Practise on a mixture of KCl, KBr, and KI.) 


1. Add to the solution a mixture of one part cupric sulphate and three parts 
ferrous sulphate, or mix the solution with excess of cupric sulphate and 
drop in sulphurous acid till precipitation ceases. The iodide will separate 
as cuprous iodide—Cu,I,—leaving the bromide and chloride in solution. 
Unless carefully done, this separation is not absolutely accurate. 

2. Add to the solution palladious nitrate until precipitation ceases. Filter out the 
palladious iodide which separates, and pass sulphuretted hydrogen through 
the liquid to remove excess of palladium, and again filter. Boil to expel the 
excess of H,S, and the bromide and chloride remain in solution. 


54 DETECTION, ETC., OF ACIDULOUS RADICALS. 








62. DETECTION OF AN IODATE IN AN IODIDE. 
(Practise on a solution of iodine in heated potassium hydrate—KI + KIO3.) 


When excess of tartaric acid is added to potassium iodate, iodic acid is set 
free ; and when the same acid is added to potassium iodide, hydriodic acid 
is set free, and potassium hydro-tartrate formed. Thus :— 

5KI+ KIO; + 6H,C,H,.O, = 5HI + HIO; + 6KHC,H,O,. 

If these acids be thus liberated together, they immediately decompose, 

forming water and free iodine :— 
5HI + HIO; = 31, + 3H,0. 

If therefore starch paste and tartaric acid be added to pure potassium 
iodide no coloration takes place, because only hydriodic acid is liberated ; 
but if the sample contains potassium iodate, an immediate production of 
free iodine ensues, which turns the starch blue. 


63. DETECTION OF A SOLUBLE SULPHIDE IN PRESENCE OF A 
SULPHITE AND A SULPHATE. 


(Practise on mixed solutions of Na,S, Na,SO3, and Na,SQO,. 


Pour the solution on a little cadmium carbonate—CdCO;—filter, and treat 
the insoluble matter with acetic acid to remove any unacted-upon cadmium 
carbonate. If a sulphide have been present, a yellow residue of cadmium 
sulphide will remain insoluble in the acetic acid, while cadmium sulphite and 
sulphate will be found in the first filtrate, if these two radicals were present. 


64. SEPARATION OF THIOSULPHATES FROM SULPHIDES. 


(Practise on solution of commercial hyposulphite of soda, to which a drop of 
NH,HS has been added.) 


Having obtained a good preliminary idea by heating with H,SO,, add to 
a portion of the original solution—ZnSO,—in excess, and filter. 
(a) Precipitate white, and soluble in HCl, with smell of H,S 
= Sulphides. | 
(2) A portion of filtrate heated with H,SO, deposits S and smells of 
SO, ; and another portion added to a drop or two of ammonio- 
cupric sulphate instantly causes decolorisation. 
= Hyposulphites. 


65. SEPARATION OF SULPHIDES, SULPHITES, and SULPHATES, 


(Practise on mixed solutions of sodium sulphite and sulphate, to which a 
drop of NH,HS has been added.) 


Pour the solution on an excess of cadmium carbonate, digest at a gentle 
heat, filter, and examine the precipitate for a sulphide as already directed (63), 
The filtrate, which may contain the sulphite and sulphate, is precipitated by 
barium chloride, the insoluble precipitate filtered out and boiled with a little 
hydrochloric acid, which will dissolve the barium sulphite with evolution 
of sulphurous anhydride—SO,—and leave the barium sulphate insoluble. 


66. SEPARATION OF SILICIC ANHYDRIDE (SILICA) FROM ALL 
OTHER ACIDS. 


(Practise upon powdered glass.) 


Fuse the substance with a large excess of KNaCO, in a platinum crucible, 
and when all action has ceased, cool, and boil the residue with water. The 


DETECTION OF NITRITES, NITRIC ACID, ETC. 55 





silica passes into solution with the other acid radicals, and the metals are left 
as oxides. Acidulate the solution with hydrochloric acid, evaporate to dry- 
ness, and heat the residue to 280° Fahr., and maintain the heat for some 
time. Drench the residue with strong hydrochloric acid, then add water, 
and boil, when the silica will alone remain insoluble. 


67. DETECTION OF A NITRITE IN THE PRESENCE OF A NITRATE. 


(Practise upon potassium nitrate which has been slightly heated so 
as to partially decompose it). 


Add a little potassium iodide and starch paste, then introduce a small 
pinch of powdered metallic zinc, and lastly acidulate with acetic acid, when, 
if a nitrite be present, a blue colour will be produced, due to the liberation 
of iodine. ‘This test is often a very necessary one when dealing with drinking 
water, the presence in which of nitrites, derived from the oxidation of 
comparatively recent organic contamination, is a dangerous indication. 


68. DETECTION OF FREE NITRIC ACID IN THE PRESENCE OF A 
NITRATE. | 


Digest with excess of barium carbonate; filter, and add to the filtrate some dilute sulphuric 


_acid, when, if the free acid were present, a precipitate of barium sulphate will be produced. 


This test is only good in the insured absence of any other acid capable of dissolving barium 
carbonate. It will also serve for detecting free hydrochloric and acetic acids in presence of 
their salts. 


69. DETECTION OF A NITRATE IN THE PRESENCE OF AN IODIDE. 
(Practise upon mixed solutions of potassium nitrate and potassium iodide.) 


The fact that the addition of strong sulphuric acid liberates iodine renders 
the proof of a nitrate by the ordinary iron process doubtful in the presence 
of iodides and bromides. In this case proceed by one of the following 
methods :— 

1. Boil with excess of potassium hydrate until any ammonium salts 
are decomposed, then add a fragment of zinc and again boil. 
Any nitrate present will be converted into ammonia, which 
may be recognised in the steam with moistened red litmus 
paper. 

2. Warm with a little zinc amalgam and add a little acetic acid and 
starch paste, when the nitrate, being reduced to nitrite, will 
cause the liberation of iodine, and colour the starch paste blue. 

3. Boil with stannous chloride and a large excess of hydrochloric acid, 
which will produce ammonium chloride from a nitrate ; and 
by boiling the liquid with excess of potassium hydrate, the 
ammonia gas may be evolved. Of course the absence of 
ammonium salts must be first insured. 


70. SEPARATION OF CHLORIDES, IODIDES, and BROMIDES FROM 
NITRATES. 


Digest with argentic sulphate, which will precipitate the halogens as silver 
salts and leave the nitrate in solution. : 
71. SEPARATION OF CYANIDES FROM CHLORIDES. 
(Practise on a mixed solution of KCN and KC.) 


Acidulate slightly with nitric acid, add excess of argentic nitrate, wash the 
precipitate thoroughly with boiling water by decantation, allow it to settle 
completely, pour off all the water, and boil with strong nitric acid, when the 


56 DETECTION, ETC., OF ACIDULOUS RADICALS. 





argentic cyanide is decomposed, leaving the chloride insoluble. The solution 
in nitric acid is diluted and hydrochloric acid added, when any dissolved 
silver is detected by precipitation, as chloride, thus indicating the presence of 
argentic cyanide in the original mixture. 


72. SEPARATION OF FERRO- FROM FERRI-CYANIDES. 
(Practise upon mixed solutions of potassium ferro- and ferri-cyanides.) 


Acidulate with hydrochloric acid, add excess of ferric chloride, warm 
gently ; the ferrocyanide will be precipitated. Pour off some of the brownish 
liquid and heat with a little zinc amalgam, when a blue precipitate will form, 
owing to the reduction of the ferri- to ferro-cyanide. 


73. DETECTION OF CYANIDES IN THE PRESENCE OF FERRO- 
AND FERRI-CYANIDES. 


(Practise upon mixed solutions of potassium cyanide and ferrocyanide.) 


Acidulate slightly with nitric acid and add an excess of a mixture of ferrous 
and ferric sulphates ; warm gently, and allow the precipitate to subside. Pour 
off a little of the supernatant liquid, add to it excess of potassium hydrate, 
and then acidulate with hydrochloric acid, when the production of another 
blue precipitate will prove the cyanide. 


74, DETECTION OF A PHOSPHATE IN THE PRESENCE OF CALCIUM, 
BARIUM, STRONTIUM, MANGANESE, AND MAGNESIUM. 


Practise on ordinary ‘‘ phosphate of lime.” 
y ~ phosp 


Dissolve in water by the aid of the smallest quantity of nitric acid, then add 
excess of ammonium acetate, which will remove the excess of nitric acid with- 
out rendering the solution alkaline. In this solution the phosphate may be 
proved by adding a drop or two of ferric chloride and warming, when a white 
precipitate of ferric phosphate—Fe2(PO,4)2—will form, insoluble in the acetic 
acid liberated. . 


75. DETECTION OF A PHOSPHATE IN THE PRESENCE OF IRON. 
(Practise on ordinary “ phosphate of iron.”) 


Dissolve in the smallest possible quantity of hydrochloric acid, add some 
citric acid, and then excess of ammonium hydrate. By this means an alkaline 
liquid is obtained, owing to the power of the organic acid to prevent the pre- 
cipitation of the metal by the ammonium hydrate; and in this liquid, when 
cold, magnesia mixture (ammonio-sulphate of magnesia) causes the precipitation 
of white crystalline magnesium-ammonium phosphate. 


76. SEPARATION OF AN ARSENIATE FROM A PHOSPHATE. 


This can only be done by acidulating with hydrochloric acid, and passing a 
slow stream of sulphuretted hydrogen through the solution for several hours, 
until the whole of the arsenic is removed. 


‘7%. DETECTION OF A FORMATE IN THE PRESENCE OF FIXED 
ORGANIC ACIDS WHICH REDUCE SILVER SALTS. 
Distil with dilute sulphuric acid at the heat of a water bath, neutralise the © 


distillate with sodium carbonate, add a séight excess of acetic acid, and boil 
with argentic nitrate, when a dark deposit of metallic silver will form. 


SEPARATION OF OXALATES, TARTRATES, ETC. oe; 





78. SEPARATION OF OXALATES, TARTRATES, CITRATES, and 
MALATES. 


(Practise upon mixed solutions of oxalic, tartaric, and citric acids.) 


If the solution be acid, neutralise it with sodium hydrate; but if neutral or 
alkaline it is ready for use, and is treated as follows :— 

A, Acidulate slightly but distinctly with acetic acid, bring the whole 
to the boil, and add a drop or two of calcium chloride; and if 
it produce a precipitate, add it till precipitation ceases. Keep 
the whole nearly boiling for a time, till the precipitate aggre- 
gates, and filter. This precipitate is calcium oxalate, and it 
should be quite insoluble in cold solution of KHO. 

B. To the filtrate from 4, mixed with some more calcium chloride, 
ammonium hydrate is added in slight but distinct excess, 
and the whole thoroughly cooled. Calcium tartrate precipi- 
tates, and when it has settled clear, the liquid is poured off 
and preserved for C. This precipitate, after washing, should 
be entirely soluble in cold solution of potassium hydrate, and 
reprecipitable by boiling. 

C. The liquid is slowly boiled for some time ; and if a precipitate does 
not form readily, a little more CaCl, and NH,HO added, and 
the boiling resumed. The precipitate, when it begins to subside 
well, is filtered out whilst still hot. It should be (after washing) 
quite insoluble in cold solution of potassium hydrate ; but 
soluble in perfectly neutral solution of cupric chloride. 

D. To the filtrate add alcohol, when calcium malate will separate ; 
but this portion of the separation is not infallible, and the 
precipitate must be carefully examined to see that it really is 
malate. 


"9, DETECTION OF CARBOLIC ACID IN THE PRESENCE OF 
SALICYLIC ACID. 


Boil ro grains in half an ounce of water, cool, decant the solution, and add 
to it x minim of a saturated solution of KHCO,, 1 minim of aniline, and 5 
drops of solution of chlorinated lime, when, if carbolic acid be present, a deep 
blue is produced. 


CHAPTER 


QUALITATIVE ANALYSIS, AS APPLIED TO THE DETECTION 
OF UNKNOWN SALTS. 


§ I. GENERAL PRELIMINARY EXAMINATION. 


UNDER this head are included— 
1, The observation of the physical properties of the substance sub- 
mitted for analysis. 
2. Its behaviour when heated, either alone or in the presence of 
reducing agents or fluxes. 
3. Its reaction with test-papers ; the color it communicates to flame, 
etc. 

So particular and minute may this examination be, that in the larger works 
on chemical analysis many pages will be found devoted to it; but for the 
purposes of the analysis likely to come before the ordinary chemical student, 
it is sufficient only to carry it the length of a few readily obtainable and 
unmistakable inferences. 


Step 1. If the substance be a liquid, carefully mark its reaction with blue 

- and red litmus paper, evaporate a little to dryness at a gentle heat 

on a clean porcelain crucible lid, observing the nature of the residue 

left, if any; and finally raise this residue to a red heat, carefully 

noting whether it is volatilised, blackened, or altered in color any 

way. Ifa solid, heat it directly to redness on a crucible lid (or in 

a dry test tube), and note effect; then shake a little up with distilled 
water, and note its reaction with blue and red litmus paper. _ 


From a careful study of these points, the following simple inferences may 
safely be drawn ; any appearance not herein referred to being neglected as not 
affording a really distinctive indication. 


A. Neutral, no odor, and leaving no residue whatever. Probably 
water. 

&. Strongly acid, leaving no residue. Probably an ordinary volatile 
acid, such as HCl, HNO,, HC,H,0,, etc. 

C. Strongly acid, leaving a residue, fusible by heat and also strongly 
acid. Probably a non-volatile mineral acid, such as H,PQx,. 

D. Strongly acid, leaving a residue, which on heating chars, and 
entirely burns away. Probably free organic acid, such as 
H,C,H,O,, H;C,H;0,, HC,H,0,, etc. 

Note.—Oxalic and formic acids do not char, 

£. Neutral or slightly acid, leaving a residue, which volatilises in 
fumes, but without blackening. Probably an ordinary salt of 
a volatile metal, such as NH, Hg, As, Sb, etc. 

fF, Neutral or slightly acid, leaving a residue which on heating 
blackens and volatilises in fumes. Probably an organic salt 
of NH,, Hg, or other volatile metal. 


Note.—In this case it is best at once to test the original for NH, or Hg by boiling 
with KHO and SnCl, respectively. 


GENERAL PRELIMINARY EXAMINATION. 59 





G. Neutral or slightly acid, leaving a residue, which on heating 
changes color as follows :— 


Yellow while hot, white on cooling. Probably salt of Zn. 

Deep yellow while hot, yellow on cooling. Probably salt of Pb. 

Yellowish-brown while hot, dirty light-yellow on cooling. Pro- 
bably salt of Sn’. 

Orange or red while hot, dull yellow on cooling. Probably salt 
of Bi. | 

Red while hot, reddish-brown on cooling. Probably salt of 
re.or Ce, 

Permanent brownish-black. Certain salts of Mn. 


H. Neutral or slightly acid, leaving a white residue, which blackens 
on heating, burns, and leaves a black or greyish mass. Pro- 
bably an organic salt of a fixed metal. J this spectal case, 
proceed as follows :— 


Moisten the residue with a little water, and touch it with reddened litmus 
paper. If alkaline, the original substance was an organic salt of K, Na, or 
Li, in which case proceed by (a). If not alkaline, proceed by (#). 

(a) Boil the ash with the smallest possible quantity of water, filter, acidulate with 
HCI till effervescence ceases; dip a perfectly clean platinum wire in the solu- 
tion, and try the flame test. Ifcrimson, Li. Bright yellow, Na. Violet, K. 

Note.—The latter flame not being very easily seen in the daylight, it is advisable to 
add to the solution PtCl, and C,H,O. Shake well and cool. Yellow crystal- 
line precipitate of potassium platinochloride—PtCl,2KCl. 

(2) The ash is covered with water and treated with HC,H,O,. If effervescence takes 
place, the original substance was probably an organic salt of Ba, Sr, or Ca; 
and these metals may at once be tested for in the acetic acid solution. 

Note.—Oxalates, although organic, do not blacken to any extent. If carefully 
observed, however, a slight greyish tint, followed by a distinct glow running 
through the mass, will be noticed at the moment of decomposition. To make 
certain, it is well to place a little of the original powder in one tube, and the 
residue, after ignition, in another ; cover them both with water, and add a drop 
of acetic acid to each. If the residue effervesce, and the original powder does 
not, strong presumptive evidence is obtained of the presence of an oxalate 
of the alkaline or earthy metals. : 


J. Neutral or slightly acid, leaving a residue, which takes fire and 
continues to burn even after removal from the flame, giving off 
clouds of white fumes and leaving a fixed white or pinkish 
residue. Probably a hypophosphite ; which fact should be 
noted as an aid to future information as to acidulous radicals. 


R. Strongly alkaline, leaving a fixed white residue, also alkaline. 
A hydrate, carbonate, bicarbonate, phosphate, arseniate, borate, 
or sulphide of a fixed alkaline metal, or a hydrate or oxide of 
Ba, Sr, or Ca. In this case proceed as follows :— 


Acidulate a portion of the original solution with HCl. 

(a) If it effervesces without smell, and is therefore a carbonate or bicarbonate, test 
at once by the flame for K, Li, Na, and also another portion of the original 
solution with HgCl,. If red, a carbonate: if not, a bicarbonate. 

(d) Effervesces with smell of H,S. In this cases it is a sulphide ; and if a deposit 
of S also takes place, a polysulphide. Add to a fresh portion of the original 
solution excess of HCl, boil till H,S is expelled, filter, if necessary, and test 
the solution for all metals of fourth and fifth groups. 

(c) Effervesces with smell of HCN. Probably an alkaline cyanide such as KCN. 

(d) It does not effervesce. In this case add to a fresh portion of the original solution, 

AgNO. Ifa brownish-black precipitate be formed, it is a soluble hydrate. A 
portion of the original solution should be neutralised with HCl, and then 
examined for all metals of fourth and fifth groups. 

Note.—If AgNO, with original solution gives a yellow, a white, or_a brick-red 
precipitate, the presence of a phosphate, borate, or arseniate of K or Na may 
be suspected. In the case of a complex solution in which a salt of some other 
metal is given dissolved in excess of an alkali, an intimation of the fact will be 


60 QUALITATIVE ANALYSIS. 


obtained on cautiously adding the HCl, as, at the moment of neutralisation, the 
dissolved substance appears as a precipitate before again dissolving in the excess 
of HCl. Basic plumbic acetate has an alkaline reaction. 
Step 2. Dip a clean platinum wire in the solution, or, if a solid, moisten the 
wire with HCl, dip it in the powdered substance, and heat in the 
inner Bunsen or blowpipe flame. The outer flame is colored as 


under :— 
Violet ; . Potassium. 
Golden-yellow . . Sodium. 
Yellowish-green . . Barium. 
Crimson . : . Strontium or Lithium. 
Orange-red ; . Calcium. 
Green ; : . Copper or Boracic acid. 
Blue . : : . Lead, Arsenic, Bismuth ; 


also Copper as chloride. 


Step 3. Heat a little of the solid substance (or the residue left on evapora- 
tion if in solution) on charcoal before the blowpipe. 

Ordinary alkaline salts fuse and sink into the charcoal ; some decre- 
pitating (example NaCl, etc.), others deflagrating (as KNOs3, KCIO3, 
etc.), but no sufficiently characteristic indications are usually obtained, 
except in one of the following cases :— 

A. A white luminous residue is left. Moisten it when cold with a 
drop or two of cobaltous nitrate, and again apply the blowpipe, 
observing any change of color as follows :— 

The residue becomes blue, indicating Al, Silicates, Phosphates, 
or Borates. 
% 99 tao RL OCLe aan: Zn. 
a », pink or flesh-colored, indicating Mg. 

B. A colored residue is left. Prepare a borax bead, and heat a little 
of the substance in it, both in the reducing and oxidising flame, 
and note any colors corresponding with the following list :— 


IN OXIDISING FLAME. IN REDUCING FLAME. 


Green (hot). Blue (cold). Red (cold). 
Blue. Blue. 


Green. Green. 

Red (hot). Yellowish (cold). Bottle-green. 

Amethyst. Colorless. 
Reddish-brown (hot). Yellow (cold). | Same as oxidising flame. 





C. A metallic residue is left, with or without incrustation surrounding 
it. Mix a little of the substance with KCy and Na,COs, and 
expose on charcoal to the reducing charcoal flame. 

(a) Metallic globules are produced without any surrounding incrusta- 
tion of oxide. This occurs with Ag, Au, Cu, Fe, Co, and Ni, 
all easily recognisable. 

(6) Metallic globules are produced with a surrounding incrustation of 
oxide. This occurs with Sn, Bi, Pb, and Sb; the incrustation 
having the characteristic colours already described in Case L., 
Step 1, G. 

Note.—Sb often forms a white and distinctly crystalline crust. 

(c) The metal volatilises, and only leaves an incrustation of oxide. 
This occurs with As (garlic smell and white incrustation), 
Zn (yellow [hot], white [cold]), and Cd (reddish-brown). 


il Wade vind = or 


DETECTION OF METALS IN SALTS. 61 


Ee ee Ne aaa Ea a 


§ II. DETECTION. OF THE METAL PRESENT IN ANY SIMPLE 
SALT. 


Step 1. Preparation of the solution for analysis for the metal, if the 
substance be not already dissolved. 


1. Take a minute portion of the substance and boil it with water in 
a test-tube; should it dissolve, then take a large portion and 
dissolve for testing. | 

2. Should the salt prove insoluble, take another small portion and heat 
with HCl, and add a little water and again heat. If it now 
dissolves, prepare a larger quantity of the solution for use in 
the same manner. 

3. Should it resist HCl, try another small portion with HNO, by 
heating, and then adding water. If this dissolves it, make up 
a larger quantity of a similar solution for testing. 

4. Should HNO; also fail, try another small portion with two parts HCl 
and one part HNOs, warming and diluting as before; and if it 
succeeds, make up a larger amount of solution in the same manner. 

5. If all acids fail, then take another portion of the substance, mix it 
with several times its bulk of a perfectly dry mixture of sodium 
and potassium carbonates (prepared by heating Rochelle salt in 
an open crucible until the residue thoroughly ceases to evolve 
any gases, then extracting with distilled water, filtering, evapo- 
rating to dryness, heating the residue to redness, and preserving 
for use in a stoppered bottle. This reagent will hereafter be 
shortly described as fusion mixture). Place the whole in a 
platinum crucible, and fuse at a bright-red heat; when cold, 
boil with water and save the solution thus obtained for acidulous 
radicals. ‘The insoluble matter is then to be drenched with 
strong HCl, slightly diluted and boiled, and the solution used 
for testing for the metal. Any insoluble white gritty matter still 
remaining is put down as silica. 

Step 2. Detection of the metal. 

The processes to be applied vary according to the limitation of the possible 
substances under examination, and the following tables are to be used accord- 
ingly, using the solution obtained in Step 1. Remember that even when we 
have apparently found out the metal by the table, we should always proceed to 
perfect confirmation by applying (to fresh portions of the solution each time) all 
the tests for the metal given in Chapter Lf. Unless otherwise directed, all 
confirmations referred to in the tables are intended to be tried upon fresh 
portions of the, original solution. For brevity the said solution is in the 
tables indicated by a capital 0 in thick type, and the word precipitate is 
contracted to ppt. In simple salts we go through the groups until we 
get a result, and as soon as we do so we stop and go no farther with the 
groups, but simply confirm the result obtained by special tests. 
jThe following brief instructions may aid the student to find readily the pages required for 
the full analysis of a simple salt:— 

1. Find whether soluble in H,O or in acids, or neither. 
acid = free acid or acid salt. 


. Take the reaction alkaline = complete the analysis by ‘‘ K,” p. 59. 
neutral. 


& 


. 


; does not char = inorganic salt. 
3. Heat dry ina test-tube ae char = organic salt. See ‘*H,” p. 5% 
4. Find the metal by p. 64. 
solubility table, p. 82. 
5. Find the acid radical by If K, Na, tables pp. 76 to 80, if inorganic. 
Li, or NH,f§ ,,_ p. 80, if organic. 
6. Name the salt and write its chemical formula. 


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DETECTION OF UNKNOWN SALTS. 65 


§ III. DETECTION OF THE METALS IN COMPLEX MIXTURES OF 
; TWO OR MORE SALTS. 


Step I. Preparation of the solution for analysis in cases where the 
substance for analysis is not given in solution. 


Note.—By carefully applying this step and intelligently judging the results, we can 
often reduce a separation of two salts to the performance of two separate 
simple analyses, and so save much time and trouble. 


1. Boil some of the powdered substance with distilled water, and filter 
off from any insoluble matter. 

Evaporate a drop or two of the filtrate to dryness, at a gentle heat, on a 
slip of clean platinum foil, and if any residue be left, then save the balance 
of the filtrate for analysis as representing the portion of the original (if any) 
that is soluble in water. 

2. If anything remains insoluble from water, then wash it on the filter 
with boiling water until a drop of the washings leaves no marked 
residue on evaporation. Rinse the insoluble off the paper into 
a tube, and add hydrochloric acid drop by drop (noting carefully® 
any effervescence or odor as indicating the presence of certain 
acidulous radicals, such as carbonates, sulphides, sulphites, 
cyanides, etc.), and warm. | 

If it now all dissolves, save the fluid for analysis. If not,.then separate 
the insoluble, test the filtrate by evaporation of a drop or two, to see whether 
anything has dissolved, and if so, save the fluid for analysis as representing 
the metals present in the form of salts insoluble in water, but soluble in HCl. 

Note.—This division of any mixture into salts soluble and insoluble in water gives 
the greatest assistance in the subsequent testing for the acidulous radicals. For 
example, if a metal of the 5th group be found in the portion soluble in water, 
then any acidulous radical almost may be present ; while if a metal of one of 
the other groups be found, then generally speaking only a nitrate, sulphate, 
chloride, or acetate need be first searched for. If, on the other hand, the 
substance resists water and only goes into solution with HCl, then as a rule 
no metal of the 5th group ts present, and we might consider that we were 
probably dealing with a carbonate, oxide, phosphate, arseniate, oxalate, 
sulphide, sulphite, cyanide, ferro- or ferri-cyanide, or borate of a metal, not 
in the 5th group. Certain tartrates and citrates, chiefly of the 4th group, 
would also come in this category. 


3. If the substance resists both water and HCl, try nitric acid, first alone, 


and then with the addition of hydrochloric acid. 

This treatment dissolves certain metals in the free state, such as Ag, Pb, 
Bi, Hg, and Cu, and also acts upon HgCl, HgS, and other insoluble sul- 
phides, and on Fe,O, and some refractory oxides. Gold and platinum only 
dissolve in nitro-hydrochloric acid. 

Note.—When HNO, has been used as a solvent, the liquid should always be 
evaporated with HCI till all the HNO, has been displaced, then allowed to 
get quite cold and any precipitate filtered out and treated as belonging to 
the Ist group, while the filtrate is directly treated with H,S. 

4. If anything still remains insoluble, it must be fused with fusion 
mixture (KNaCO,) at a bright red. heat till action ceases, and 
the residue so obtained boiled with water and filtered. 

The filtrate is used for the detection of acidulous radicals; while the 
insoluble matter is dissolved (after washing) in nitric acid and used for 
finding the metals. The usual run of articles requiring this treatment are— 


sand, clay, and other silicates, sulphates of Ba, Sr, Ca (latter not always), 
and Pb, the haloid salts of silver, SnO, and Sb,O;. 


Step II. Proceed to apply the following tables to the prepared solution 
from Step I. 

Note.—The whole of the first table for “separation into groups” must be gone 
through, but if no effect be obtained in Groups I. or II., a fresh portion of 
the prepared solution should be taken for Group IIL, etc., so saving the 
time required for evaporating to a considerable extent. 


5 


QUALITATIVE ANALYSIS. 






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QUALITATIVE ANALYSIS. 


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‘(q) NOISIAIC “III dQOUDY JO SIVLANW AO NOLLVUVaaS 
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72 


73 


DETECTION OF UNKNOWN SALTS. 





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‘A dN0ad FO SIVIAN FO NOILVUVdgS 


Rie iid Vals 








DETECTION OF UNENOWN SALTS. 76 





§ IV. DETECTION OF THE ACIDULOUS RADICALS. 
Division A.—Preliminary Examination. 


IMPORTANT NoTE.—We must always decide what metals or bases are 
present before we proceed to test for acidulous radicals. We- 
must then note which bases are present as soluble and which 
as insoluble salts (in H,O). Lastly, we must consider what 
acids might be present in each case, and only test for such 
possible acids, because nothing leads to so many errors as testing 
Jor acids which could not possibly exist. We must also carefully 
note the information received in the former preliminary exami- 
nation, especially as regards the presence of organic matter, 
and remember that, if the original substance does not char on 
heating, we must never enter into the testing for organic actds, 
because none can possibly be present except oxalate, which is 
provided for in the inorganic portion of the course with this 
very object, together with a few others included for convenience. 
We must also remember to note what happens when we 
dissolve the original substance in HCl, provided such a step 
is necessary, and if any effervescence occurs we must be sure 
to smell the gas given off, because we may then at once detect 
the following :— 


*Carbonate . . effervescence without odor, and the evolved gas 
poured into lime-water renders it milky. 

*Sulphide . odor of H,S (with deposit of S polysulphide). 

*Sulphite ! + ae epee a fe hyposulphite). 

*Cyanide ELC IN, 

Peroxide UEC o.Lorine, 


Fe, Zn, or Sn (as metals)—no odor but hydrogen evolved. 


We must also remember that organic bodies, such as alkaloids or 
sugar, other than organic salts, might be contained in a mixture 
which would cause charring on heating, and so lead us to test for 
what was not there. It will be useful at this point to see how 
we can guard against two of the more commonly occurring of 
such cases. 


(1) Sugar. This will cause the soluble portion to be syrupy, and 
when warmed with ddute H,SO, it will rapidly darken, whereas 
organic salts, as a rule, require fairly strong H2SO, to char 
them. The solution will have a sweet taste, and after boiling 
with a drop or two of very dilute H,SO, it will reduce Fehling’s 
solution. 


(2) Alkaloids (nitrogenous organic bases). These will cause an odor 
like burning hair on heating to redness. The soluble portion of 
the mixture carefully treated with very dilute NH,HO will usually 
give a cloud (which may or may not dissolve in excess), and then 
the same liquid shaken up with chloroform, and the chloroform 
evaporated at a gentle heat, will leave the alkaloid as a residue. 
If no residue be thus obtained, then no alkaloid can be present 
except morphia, and this latter would never be put ina mixture 
unless specially intended for toxicological investigation, because 





* In soluble salts these_effects will come on:adding HCl in Group I. 


QUALITATIVE ANALYSIS. 


its detection requires altogether special work, which will be 
afterwards detailed. 

Having well considered all this, we now proceed to the actual 
work, carefully remembering that all the indications are merely 
preliminary, and that we are xot zo take notice unless we really 
get a distinct result. If we really do get one, then it may save us 
going so far through our actual acid course, but: if we are not 
certain, then it is no use attempting to persuade ourselves and 
wasting time, but we should just note the probability and then 
at once pass on to confirm by the actual course hereafter 
detailed. 

No attempt is made to describe odors, because the student 
should simply put himself through a course of training for this 
preliminary examination on known salts, and learn to recognise 
all the odors, etc. This is a most important study, and should 
be carefully stuck to, until the nose and eyes have been quite 
trained to recognise the individual effects to be expected from 
each acid. 


Step I. Put a portion of the original solution in a tube, or if it be a 
solid cover it with some water, just acidulate with dilute H,SO,, 
and look for any effervescence or odor, then boil and smell. 
The following radicals may be thus recognised :— 


Effervescence without odor . : : Carbonate. 
Sulphide. 
Effervescence with characteristic odors . fe hite. 
yanide. 
Hypochlorite. 
Red fumes . : : : p Nitrite. 


Step II. Add another drop of H,SO,, and again warm. 


Odor of vinegar . Acetate. 
52. asad a Oe Wt Ce OsiL Oto mae Hyposulphite. 
HAT eae ee LEC ie .; t Sulphocyanate. 


» 9, HCN ,, crystalline deposit, ) Ferro- or 
often bluish ; Ferri-cyanide. 
a », Walerian or sharp odor . . { Valerianate, ens 
. zoate, Succinate. 
3 St yg  Carbolie acid A : ; Carbolate. 
Note.—The effects of Step II. will often come perfectly in Step I., and 
then Step II. may be considered as part of Step I. 

Step II.:Put a little of the original solid (or the residue left on evapora- 
tion if the original was a liquid) into a dry tube, cover it 
with strong H,SO, and warm, but not sufficiently to cause the 
H,SQ, itself to fume. (See note, important to prevent accidents.) 


Thus we get :— 
Chloe. change ot atar (Tei 
White fumes | Fluoride. and coored 4 Bromide. 
(characteristic of) | Benzoate. para iM a | Bromate. 
Succinate. pect ie kh Chlorate. 


Sulpho-carbolate. 


DETECTION OF UNENOWN SALTS. 77 





Effervescence on warming only, for 5 alate Fe Tate 
which persists after withdraw- q by g 


; . ffect lime-water. 
ing from flame, but with zo wy 
darkening in color and no Oxalates—give both CO and CO,, and 


odor the gas therefore renders 
lime-water milky. 


Tartrates—rapid charring and smell 
of burnt sugar. 


Effervescence on warming, but i oe pelle so dark, and peculiar 
the liquid darkens in color toa Bee: 


greater or less extent. Citrates seis tie and peculiar 
3, Oleates—char and_ give odor of 
acrolein. 
Meconate. 
Darkening in color without any eens 
very marked effervescence. eens 


Salicylate (very slow darkening). 
No fumes—gelatinous deposit (or flaky)—Silicate. 
» 9, scaly crystals with pearly lustre—Borate (best seen. on 
cooling). 
No change takes place at all with—Sulphate, phosphate, and arseniate. 


Chromates turn orange and then green—Bichromates turn green straight 
off. 


Note Important.—On adding strong sulphuric acid to any solid, one drop 
only should be first carefully applied, because chlorates, iodates, etc., 
are apt to explode on the first touch of the acid. 


If we get a decided indication of the presence of any acidulous radical 
as above, we may at once apply confirmatory tests for the radical found to 
our original substance, and so save going through the course, especially if 
the substance be soluble in water ; but if insoluble a solution must always 
be specially prepared for acid testing. 


Division B.—Preparation of a Solution for Testing for Acidulous Radical. 


The success of the course for the detection of acids depends in the highest 
degree upon the care with which the solution is first prepared. It may be 
taken as a general rule that no testing for acids is reliable unless they are 
present in the form of salts of alkaline metals. It is therefore necessary to 
transform our acids into such salts ; and, to do this successfully, the following 
rules must be closely adhered to :— 

I. If the original is soluble in water, and adsolutely neutral to test- 
paper, you may venture as a rule to use it as it is, and this will 
also apply, if it be a/kaline, to test-paper. 

II. If the original be soluble in water, but in the least acid, we must 
drop in NaHO till it is rendered just a/kaline, boil, and, if any 
precipitate should form, filter and use the filtrate for the acid 
course, 

III. The portion insoluble in water (or the whole of the original if all 
insoluble) must be boiled with a little NaHO, then diluted, 
filtered, and the filtrate only used for the acid course. 


78 QUALITATIVE ANALYSIS. 





Note.—If Al, Zn, Sb, Sn, Cr, Pb, or any metal whose hydrate is soluble 
in excess of NaHO has been found, then we must use a solution 
of NazgCOs, instead of NaHO in both Cases II. and III. 

We must also take care to prepare plenty of our solution, 
because if the full acid course has to be gone through, we shall 
require possibly to employ eight to ten different portions before 
we have finished. 

This course now about to be explained is so devised that by working upon 
the prepared solution, in the presence successively of HCl, HNO;, HC,H3O,, 
H,SO, and absolute neutrality, we can insure the precipitation in each stage 
of certain given acidulous radicals only by reagents, which, if used without such 
precautions, would precipitate many more than they do when so employed. 


Division C.—Course for the Detection of Inorganic Acids together with 
a few Organic included for certain reasons. 


Step I. Acidulate a portion of the prepared solution with HCl, and 
then to successive portions thereof apply the following tests :— 








REAGENT. EFFECT. AciD PRESENT. 

{q)-BaCly ., ..,« 2.4 White. ppt. cimsolublesaut 
boiling HNO: % °,.. «»-.4spulphate: 
Dark blue ppt. . . | Ferrocyanide. 
Blood red color  dis- 

(2) HesSh? astanaids charged by HgCl, . . |. Sulphocyanate. 
Blood red color not dis- 

charged by HgCl, . . | Meconate. 

(c) FeSO, . .. ... | Dark blue...) .) t.gc Genie ee 
Dip in and dry over ie 

(2) Turmeric paper . gas when sth pape) | aes 


turns pink, changed | 
to green by KHO. 





Step II. Acidulate a portion of the prepared solution with HNOs, 
add excess of AgNOs3, warm and shake, disregarding any precipt- 
tate thatts not white or yellow and distinctly curdy. ‘Thus we 
get the following :— 

(a) Cyanide—Curdy white; soluble in very dilute NH,HO, and also 
in boiling HNOs. 

(6) Chloride—Curdy white ; soluble in very dilute NH,HO, but in- 
soluble in boiling HNO. 

(c) Bromide—Curdy dirty white; slowly soluble in fairly strong 
NH,HO, but not in very dilute ; insoluble in HNO. 

(Z) lodide—Curdy pale yellow ; insoluble even in strong NH,HO and 
also in HNOs. . 


Note.—Many other acids, such as ferrocyanide, oxalate, chromate, etc., are apt to come 
down with AgNO, in presence even of HNOs, but the precipitates are (if 
white) ot curdy, or they are colored red and so will be disregarded ; and we 
therefore deal only with the four acids mentioned giving curdy precipitates. 


DETECTION OF UNKNOWN SALTS. 79 





To distinguish between these four acids we— 


(z) Filter out the precipitate with AgNOs, wash it, and then percolate it 
several times with very dilute NH,HO (1 in 20), when AgCland 
AgCN will dissolve, and can be reprecipitated from the filtrate by 
FINO;, while any AgBr or, AgI will be left on the filter. 

Note.—It is very important to have the dilute NH,HO exactly 1 in 20, because, 
if stronger, then AgBr will also dissolve, and in any case a mere cloud on 
adding the ZNO; 7s to be disregarded, because if AgCl or AgCN be really 
present, they will reprecipitate in distinct curds, on adding HNO, warming 


and shaking. 

(2) If by (1) evidence of the presence of Cl or CN be obtained, then 
test a portion of the original prepared solution for CN by 
Scheele’s test, and if not present then the precipitate was all due 
to Cl. If CN be found, then another precipitate must be 
obtained by excess of AgNO,, filtered, washed, drained, and 
transferred to a tube with strong HNO; and boiled, when any 
AgCl will remain insoluble. 

Note.—As HCN is so easily smelt in the preliminary examination, we should always 
know before we begin the group whether it is there, and then if it be present 
the boiling with HNO, will be required, but if not, then we put it down at 
once as chloride if the NH,HO dissolves anything. 

(3) If, after treating with NH,HO (1 in 20), any residue be left on the 
filter, leading to the idea that AgBr or AgI may be present, we 
proceed as follows : Toa smad/ portion of our prepared solution 
a drop of mucilage of starch is added, and then one or two drops 
of chlorine water. If iodide be present we shall get a blue. 
Now we go on adding fresh chlorine water till all the blue 
has been bleached, and if the whole is now perfectly white only 
iodide is present; but if it remain at all yellow, then we add 
some chloroform and shake up, when an orange color in the 
chloroform will indicate bromide. This depends on the fact 
that free iodine combines with chlorine more readily than with 
bromine. 


Step ITI. Acidulate a portion of the prepared solution with acetic acid, 
bring it to the boil, and then test successive portions while 
boiling as follows :— 


REAGENT. EFFECT. AcID PRESENT. 


eee | White © ppt. soluble. “in 
50TH Bick A gael a tity 


Oxalate. 


(6) Fe,Cl, (zot in ) 
excess) ee 


Phosphate or 


White pptatrii.<iehis { Arseniate. 


eet | ellOW fe Chromate. 








To distinguish between phosphate and arseniate exactly 
neutralise a portion of the prepared solution with dilute HNO, 
and add AgNOs. 

Yellow soluble in NH,HO= Phosphate ° 
Red do. do. .#\=Arseniate 


80 QUALITATIVE ANALYSIS. 
i 

Step IV. Just acidulate a portion of the prepared solution with dilute 

H.SO,, then add a strong and fresh solution of FeSO,, and run 
some strong H,SO, down the side of the tube so that it collects 
at the bottom. A dark ring where the liquids meet proves 
Nitrate. 

Note.—If todide has been previously found, this test fails to be conclusive, and in such 
case we must take advantage of the power of nascent hydrogen to reduce 
nitrates to ammonia. If no salt of NH, has been found in metal testing, we 
add to some of the prepared solution a fragment of zinc and sufficient HCl 
to cause a brisk effervescence. After ten minutes we add excess of KHO 
and boil, when an odor of NH, proves Nitrate. If NH, salts be present 
we add a little KHO to the prepared solution, evaporate to dryness, heat 
the residue till no more fumes are evolved, and then dissolve in water and 
apply the zinc, etc., as above described. 

Extra Step. Iodates being very difficult to detect in the preliminary, 
it is well to test for them specially (if they can possibly be 
present) by adding to the prepared solution KI and starch 
paste, and acidulating with tartaric acid. This is not reliable in 
presence of nitrites. 


Division D.—Course for the Detection of Organic Acids. 


(Only to be entered upon in the event of the original substance being proved to 
contain organic matter by charring on heating in the preliminary examination.) 


The solution to be used is that prepared for acidulous testing, as already 
described. 


Step I. Place a minute fragment of litmus paper in a little of the prepared 
solution, and add acetic acid drop by drop with agitation until 
the paper jus¢ turns red, then take out the paper and add AgNO, 
in excess, lastly add a drop or two of very dilute NH,HO till 
the precipitate just commences to redissolve. Now warm the 
tube in the Bunsen flame, when a reduction to metallic silver, 
forming a mirror on the tube=Tartrate. 

Note.—The tube used must first be rendered chemically clean by boiling in it 
successively some dilute HNO, and then some dilute NaHO, and rinsing 


with distilled water. Formates produce the same effect, but do not char on 
heating. 


Step II. Place a minute fragment of test-paper into a portion of the 
prepared solution, and drop in dilute HCl till it jus¢ turns red, 
then dilute NH,HO till it 7zs¢turns blue again, cool thoroughly, 
add some CaCl, and shake well. If a precipitate forms (oxalate, 
tartrate, etc.), add excess of CaCle, shake, and let it stand in 
cold water for ten minutes and filter. Now add to the filtrate 
a little more NH,HO and boil gently for some time, when a 
white precipitate =Citrate. . 

Nok.—If CaCl, gives nothing in the cold, of course we simply warm for the citrate 
straight off. As oxalate, tartrate, etc., have all been previously tested for, we 
shall know, before commencing to test for a citrate, whether we need to 
separate them in the cold or simply to add the NH,HO and CaCl, and boil 
straight away. 

The addition of rectified spirit to the solution in which boiling has failed 
to indicate citrate will bring down a Ja/ate on cooling, but unless specially 
suspected this reaction is not a very certain one. 


Step III. Place a fragment of test-paper into a portion of the prepared 
solution, and if alkaline, make it exactly neutral by carefully 


DETECTION OF UNKNOWN SALTS. 81 





dropping in dilute HCl. Then apply the following tests to 
portions of this neutralised liquid :— 

(a) Prepare some neutral ferric chloride, by adding very dilute NH,HO 
to a solution of Fe,Cl, until a permanent cloud just forms, and 


filtering. 
Now add some of this reagent, and observe effect as follows :— 
Seas Carbolate 
(1) Red color peueccreute (2) Purple color f Sulpho-carbolate 
Pyrogallate ( Salicylate 
Gallate kes at Benzoate 
(3) Blue-black { er cio (4) Pinkish precipitate { Be cinate 


Notes. 

(1) Acetate, red, is instantly discharged by a drop of HCl; pyrogallate is turned 
black by excess of KHO and exposure to air. Sulphocyanate and meconate 
have been already proved in the inorganic acid course, but distinguished by 
action of HgCl, if desired. 

(2) Acidulate a portion of prepared solution with HCl and shake up with ether. 
Remove the ether by a pipette and evaporate it on a watch-glass at a very 
gentle heat. Carbolic acid is left an oily liquid readily recognised, while 
salicylic acid is left in characteristic crystals, as giving a beautiful violet 
with Fe,Cl,. (Also see page 57 for another separation.) Sulphocarbolic 
acid gives no immediate precipitate with BaCl,, but on evaporating with a 
little Na,CO, and KNO,, and fusing, then the residue dissolved in H,O shows 
a sulphate with BaCl.,. 

(3) With excess of KHO a solution of gallic acid rapidly becomes dark on exposure 
to the air, while tannic acid gives a flocculent liquid not so rapidly changing. 
Tannic acid also precipitates solution of gelatine, and gallic does not. 

(4) Take a good quantity of the neutralised and prepared solution, add excess of 
Fe,Cl,, filter out the precipitate and wash it. Now percolate it with some 
dilute NH,HO, evaporate the liquid so obtained to a low bulk, cool 
thoroughly, and acidulate with HCl. Benzotc acid will separate in silky 
crystals, and succinic acid will not. 

Step IV. If oleic, lactic, or sulphovinic (ethyl-sulphuric) acids be 
suspected, specially test for them as follows :— 

Oleic acid will have shown its presence by always floating to 
the surface as an oily liquid whenever the prepared solution is 
acidulated with any acid. To confirm and distinguish it from 
the other fatty acids (stearic, etc.) take some of the prepared 
solution and acidulate with HCl, warm and set aside till the 
oily layer floats up. Now remove the liquid beneath, as far as 
possible, with a pipette, add some water, boil and drop in small 
fragments of K,COs;, until the oily layer is saponified and 
dissolves. Now put ina piece of test-paper and carefully add 
acetic acid to exact neutrality, then cool and precipitate, with 
excess of Pb(C,H,O2),. Filter out the oleate of lead, wash it 
with boiling water, let it thoroughly drain, and then prove that 
it is soluble in ether (stearate and palmitate of lead are 
insoluble). 

Lactic acid. Acidulate the prepared solution with HCl and shake up 
with ether. Pipette off the ether into a porcelain capsule and let 
it evaporate at a gentle heat, when the acid will be left and may 
be recognised as follows: (a) A portion heated burns at first 
with a blue flame, and then the flame becomes luminous as the 
temperature rises ; (4) Another portion warmed with K,Mn,Og 
gives the odor of aldehyd. . 

Sulpho-vinates do not precipitate BaCl, in the cold, but, on boiling, 
give a precipitate of BaSO, and an odor of spirit. 

6 


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“ALITICOIOS 


82 





DETECTION OF UNKNOWN SALTS. 


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84 QUALITATIVE ANALYSIS. 


ec 


§ V.—SPECIAL PROCESSES FOR PROVING THE IDENTITY OF 
CERTAIN READILY RECOGNISABLE SUBSTANCES. 


(A) Salts of the Halogens. 


Chlorine water. Characteristic odor; entirely volatile; bleaches 
indigo; KI + starch paste gives blue ; AgNO, gives curdy 
white. 

Hydrochloric acid. Slight fumes with sharp odor and strong acidity ; 
entirely volatile ; AgNO, gives curdy white ; heated with MnO, 
evolves Cl, 


Ferric chloride in solution. Orange-red liquid, not becoming milky 
with H,O ; test for ferric iron and for a chloride. : 


Antimonious chloride in solution. Orange-red liquid, becoming milky 
when diluted with H,O; milky liquid divided; one part 
becomes orange with H,S, and the other portion, after filtration, 
gives test for chloride with AgNO. 


Mercurous chloride. -- Heavy dull white powder, entirely volatile ; turns 
grey when boiled with SnCl,, turns black when boiled with 
dilute KHO, and, after filtration, the liquid gives test for 
chloride on acidulating with HNOs3 and adding AgNOs. 


Mercuric-ammonium chloride. Opaque white powder, entirely volatile ; 
becomes grey when boiled with SnCly ; boiled with KHO turns 
yellow and gives off NH3, and the liquid, after filtration, gives 
test for chloride on acidulating with HNO, and adding AgNO3. 


Chlorinated lime. Dull white powder, having the odor of chlorine; 
shaken up*with water partly dissolves, and the solution, after 
filtration, gives with oxalic acid a white precipitate and evolves 
Cie 

Potassium chlorate. 1n crystalline plates, deflagrating on heating with 
evolution of oxygen and exploding when touched with H,sO, 
with an odor of Cl,Q,; solution gives no precipitate with 
AgNO, ; :evaporated to dryness, heated to redness and the 
residue dissolved in very little water, yields the tests for 
potassium with PtCl, and for chloride with AgNO. 


Mercurous todide. Vellowish-green heavy powder, entirely volatile ; 
heated gently in a dry tube gives sublimate of Hgl,, leaving a 
globule of metallic Hg. 


Mercuric iodide. A bright scarlet powder turning yellow and then 
volatilising when gently heated on a piece of paper; boil 
with dilute KHO, let settle, and pour off, when the liquid 
gives blue with starch paste and HNOs, while the insoluble 
portion dissolved in HCl and boiled with SnCl, gives grey. 


(B) Oxides, Carbonates, ete. 


Hydrogen peroxide. Colorless liquid, odor like weak chlorine water ; 
gives a blue with KI and starch paste, and the resulting liquid 
is alkaline to test-paper ; no precipitate with AgNO,, blue with 
Fe,Cl, and K,Fe,Cyi, (detects 1 in 10,000,000). 


SPECIAL PROCESSES. 85 


Barium oxide or hydrate, and Calcium. oxide or hydrate. Whitish 
powders which, when shaken up with a Z¢¢//e water, do not appear 
to be soluble, but render the liquid strongly alkaline; add more 
water, shake and filter, and apply to the filtrate the tests for Ba 
and Ca, and in another portion prove soluble hydrate by getting 
a brown with AgNO3; heated in a dry tube give off moisture 
if hydrates, but not if oxides. 


Magnesium carbonate or oxide. Light white powders not changing 
color on heating; dissolve in dilute HCl (former effervesces, 
latter not), and then apply tests for Mg by adding 
NH,Cl1+(NH,),CO; and getting no precipitate, and lastly 
adding Na,HPO, and getting a white precipitate. 


Zinc carbonate or oxide. White powders turning yellow while hot and 
white again on cooling; dissolve in dilute HNO, (effervescing 
or not), and apply tests for Zn. 


Plumbic carbonate. Heavy white powder, turning yellow on heating ; 
dissolved in smallest possible excess of HNOs effervesces, and 
the solution diluted with H,O does not become milky; apply 
tests for Pb. 


Plumbic oxide. Yellow or flesh-colored powder, heavy, and becoming 
yellow on heating; dissolves in HNO3: without effervescence, 
and otherwise behaves as the carbonate. 


Red lead. Heavy red powder turning yellow on heating, but ot 
volatile; heated with dilute HNO, turns brown, and liquid 
poured off gives tests for Pb. 


Plumbic peroxide. Puce brown powder, turning yellow when heated ; 
heated with HCl evolves Cl,, and the residue dissolved in 
boiling water gives yellow with K,CrOQ,. 


Bismuth oxycarbonate and oxide. Former white powder, latter lemon- 
yellow, and both turning deep orange while hot and pale yellow 
on cooling ; dissolve in smallest possible excess of HNO, when 
former slightly effervesces and latter not, and. the solution 
diluted with H,O becomes milky, proving Bi. 

Ferric oxide. Reddish-brown: powder unchanged by heat; dissolves 
in HCl without effervescence or odor, and the solution diluted 
gives the tests for Fe, Hydrated ferric oxide heated in a dry 
tube gives off moisture. 


Ferroso-ferric oxide. Blackish-brown powder, turned! lighter by heat ; 
dissolves in HCl without effervescence or odor, and solution 
diluted gives tests for both Fe and Fe». 


Potassium permanganate. Violet needles or prisms, giving off oxygen 
when heated and leaving a residue which when moistened is 
alkaline to test-paper; gives a fine violet solution turned 
colorless when warmed with HCl and spirit, the resulting liquid 
giving the tests for K and Mn. 


Potassium bichromate or chromate. The former is in orange crystals, 
evolving oxygen when heated, and the latter is in yellow crystals 
unaltered by heat. Both give the tests for chromate with 
AgNO3 and Pb(C,H30,),, and when heated with HCl and 
spirit both turn green and the resulting liquid gives the tests for 
Cr and K. | 


86 QUALITATIVE ANALYSIS. 





Chromic anhydride. In crimson needles, giving off oxygen when 
heated and leaving green Cr,O;. A solution mixed with dilute 
spirit gives off the odor of aldehyd, and forms a deposit of 
green CrgQz. 


Antimonious oxide. A greyish-white powder, readily fusible by heat ; 
insoluble in HNO, but soluble in heated strong HCl; the 
solution diluted with H,O becomes milky and then turns 
orange with H,s. 


Mercuric oxide. A yellow or red powder entirely volatile by heat ; 
heated in a dry tube gives off oxygen and forms a sublimate of 
metallic Hg; dissolve in dilute HCl and apply tests for Hg. 


Argentic oxide. An olive-brown powder, giving off oxygen and leaving 
metallic silver when heated ; dissolve in dilute HNO; and apply 
the tests for Ag. 


(C) Sulphates, etc. 


Sulphur. A yellow or yellowish-white crystalline amorphous powder, | 
which when heated takes fire, forms SO,, and entirely burns 
away; insoluble in H,O; boiled with HNO, dissolves with 


evolution of red fumes, and solution diluted gives white with 
BaCle. 


Sulphuretted hydrogen water. Colorless solution with odor of H,S 


and entirely volatile by heat; gives black with Pb(C,H30,)., 
etc: 


Potassium polysulphide. A greenish deliquescent solid, forming a 
greenish-yellow solution, having the odor of H,S. Acidulated 
with HCl and boiled gives off H,S, deposits Sa, and the solution 
gives test for K with PtCl, 


Kermes mineral. (Antimony sulphide, etc.) An orange-red powder, 
which when heated burns, giving off SO, and leaving a lighter- 
colored residue ; entirely soluble in NaHO; soluble in boiling 
HCI with evolution of H,S, and this solution diluted becomes 
milky and turns orange on adding HS; original powder boiled 
with solution of KHC,H,O, partly dissolves, and the solution 
gives tests for Sb. 


Sulphurous acid. Colorless liquid having odor of SO, and entirely 
volatile by heat ; BaCl, gives no precipitate, or only a slight one, 


but on adding chlorine water a dense precipitate is produced by 
BaCl,. 


Sulphuric acid. A heavy, colorless, strongly acid liquid, which evapo- 
rated on a piece of paper chars it; entirely volatile by heat; 
BaCl, gives white precipitate ; when diluted, dissolves metallic 
zinc with effervescence. 


Mercuric sulphate. White crystalline heavy powder, entirely volatile by 
heat ; treated with water forms a yellow insoluble powder, the 
liquid poured off from which gives white with BaCl, ; the yellow 
powder, dissolved in HCl, gives the tests for Hg. 


SPECIAL PROCESSES. 87 





(D) Borates, Nitrates, Phosphates, ete. 


Borie acid. In minute tabular crystals, not volatile by heat, but 
fusible to a glassy residue which is acid to moistened test-paper ; 
not appreciably soluble in cold water ; soluble in rectified spirit 
and the solution burns with a green flame. 


Nitric acid. A fuming liquid strongly acid and volatile by heat ; 
warmed with metallic copper gives off red fumes. 


Bismuth oxy-nitrate. Heavy white powder, turning orange on heating 
and becoming pale yellow on cooling ; insoluble in water, but 
soluble in HNOs, and the solution diluted becomes milky ; dis- 
solved in equal parts H,SO, and H,O, and a cold solution of 
FeSO, gently poured over the mixture, the characteristic nitrate 
ring is produced. 


Calcium and sodium hypophosphites. “White granular powders which 
on heating take fire, giving dense white fumes; if heated on 
platinum foil, go through it; dissolve and apply tests for Ca, 
Na, and hypophosphite. 


Phosphoric acid. Colorless strongly acid liquid, leaving on evapora- 
tion a non-volatile glassy residue, also acid to moistened test- 
paper; no precipitate with AgNO3, but on carefully adding 
NH,HO a yellow precipitate is formed. 


Calcium phosphate. A light white powder unaltered by heat ; soluble 
in dilute HNOs, such solution giving a gelatinous precipitate 
with NaHO, insoluble in excess, but soluble in acetic acid ; the 
solution so obtained, when divided, gives, in one part, a white 
with (NH,),C,O,, and in the other a gelatinous white with 
Fe,Cl,. 

Ferrous phosphate. A slate-blue powder turned reddish by heat; 
insoluble in H,O but soluble in HCl; a portion of this solution, 
diluted and divided, gives the tests for iron, and the remainder 
mixed with tartaric acid and then with excess of NH,HO gives 
a clear liquid which in turn yields a white precipitate with 
magnesia mixture. 


Arsenious acid. A heavy white crystalline powder entirely volatile by 
heat, slightly soluble and feebly acid ; HCl + HS gives reaction 
for arsenic; AgNO3 and CuSO, give no precipitates, but on 
carefully dropping in very dilute NH,HO a yellow and a green 
precipitate are respectively produced. 


Ferrous arseniate. A pale yellowish-green powder turned dark red by 
heat ; dissolved in HCl gives tests for Fe; boiled with dilute 
KHO and filtered, the filtrate after exact neutralisation by dilute 
HNO, gives a red precipitate with AgNO. , 


(Z) Organic Salts. 


Salt of sorrel (Potassium binoxalate). A white crystalline powder 
burning when heated, but not charring to any extent, and 
leaving an ash that is alkaline to moistened test-paper; the ash 
dissolved in HCl gives test for K with PtCl,; the original 
dissolved in water by the aid of NH,HO gives the test for 
oxalate with CaCl. ay 


88 


QUALITATIVE ANALYSIS. 


Cream of tartar (potassium bitartrate). A white gritty powder, 
charring by heat and leaving a black ash, which is alkaline to 
moistened test-paper; the ash is tested for K as in the last 
case; the original heated with H,SO, chars strongly and gives 
the odor of burning sugar. 


Rochelle salt and neutral potassium tartrate. Both are freely soluble 
and char when heated, leaving an alkaline ash; a strong cold 
solution acidulated with acetic acid lets fall a crystalline pre- 
cipitate of KHC,H,O,, and the supernatant liquor gives with 
the former a yellow and with the latter a violet flame test. 


Tartar emetic (potassium antimony] tartrate). Chars on heating, 
leaving an alkaline ash; solution acidulated with HCl gives a 
white cloud soluble in excess, and H,S then gives an orange 
precipitate; the original gives the tests for a tartrate. 


(#) Organic Compounds. 
(2) Fluids. 


Alcohol, Add K,Cr,O, and H,SO, and boil, and get a green color 
and odor of aldehyd; heat with NaC,H,O, and H,SO, and 
get odor of apples; warm with KHO and iodine, and get 
yellow precipitate of iodoform (Lezben’s test—best done on a 
portion that has been distilled off from the original liquid). 


Chloroform. Reduces Fehling’s solution. Boiled with KHO and a 
fragment of resorcin gives an intense red (vosolic acid); adda 
drop of aniline to some alcoholic solution of KHO, then adda 
drop or two of the suspected liquid and boil, when a fearfully 
offensive odor of phenyl-isocyanide is produced. 


Glycerine. A borax bead dipped in glycerine and held in the flame 
turns green; if the original liquid be acid it must be first 
neutralised and ammonium salts must be absent; add some 
solution of CuSQ,, and then add excess of NaHO, when a deep 
blue solution is obtained. Before these tests are used for any 
mixture, it should be evaporated to dryness under 100° C., 
and the residue having been extracted with ether, the ethereal 
solution should be evaporated and the tests applied to the 
residue. 


Paraldehydum (paraldehyd). Characteristic odor, soluble in water 
1 in 10; miscible with ether; no color with KHO after 
standing (distinction from ordinary aldehya). 


(5) Solids. 


Acetanilide (antifebrin). Slightly soluble in cold water, freely in 
chloroform ; heat 20 c.c. of an aqueous solution with 4 c.c. 
of strong H,SO,, until a yellow color is produced, and then 
let a few drops of this solution trickle down the side of a test 
tube half filled with chlorine water, when the bottom layer will 
be violet, and the upper one green. Heated with solution of 
KHO and a drop of chloroform, the odor of phenyl-isonitrite 
is developed. KNO,+ HNO, give red (distinction from 
phenacetin), A cold solution gives no color with Fe,Cl, 
(distinction trom antipyrin). No color with H,SO, 


SPECIAL PROCESSES. 89 





Adeps Lane (cholesterin—fat). Insoluble in water, soluble in chloro- 
form. The chloroformic solution poured gently over the surface 
of strong H,SQ, gives a purple ; five grains in ethereal solution 
mixed with phenol-phthalein gives a red on the addition of 
‘2 c.c. of normal sodium hydrate (distinction from ordinary 
fatty acids, which would saponify and absorb much more soda). 
Soluble in boiling alcohol, and crystallises out on cooling. 


Aloin. Yellow and slightly soluble in cold water, freely in hot; 
insoluble in ether. HNO, gives a red (except with socaloin, 
which goes brownish). Dissolve in strong H,SO, and a few 
drops HNO,, dilute with water, and get a yellow, turned deep 
claret by excess of NH,HO. H,SO,; ona fragment of aloin, 
and a rod moistened with HNO, held near, gives a blue with 
nataloin only. 


Chloral hydrate. Soluble in water. Heated with solution of KHO 
gives odor of chloroform, and the contents of the tube give 
the reactions of a formate (page 46). Warmed with AgNO; 
and NH,HO in a chemically-clean test tube, a mirror is produced 
in the tube. Gives the same test with resorcin as chloroform. 
Mixed with a five per cent. solution of carbolic acid, and an 
equal bulk of H,SO, added, gives a pink. 


Chrysarobin. A brownish-yellow powder, partly volatile by heat with 
yellow vapors ; insoluble in water, but soluble in KHO, gradu- 
ally producing a brilliant red. H,SO, on a fragment gives a 
reddish-brown. 


Elaterin. In greenish-white friable masses. Insoluble in water, but 
soluble in chloroform. With a drop of liquefied carbolic acid 
and two drops of H,SO, gives first crimson and then scarlet. 


Gelatinum (gelatine). Swells up in water, soluble on boiling. Tannic 
acid gives a flocculent precipitate; HgCl, gives a white ; not 
precipitated by dilute acids, alum, plumbic acetate, or ferric 
chloride. 


Glusidum (saccharine or benzoyl-sulphonic imide). Not readily soluble 
in cold water or in chloroform ; heated to redness with Na,COg 
it chars and gives off an odor of benzine ; not blackened by 
H,SO,; on adding a small fragment of resorcin and a few 
drops of H,SO, and heating, the color changes successively 
to yellow, red, and green, and SO, is given off with effervescence ; 
KHO now added gives a green fluorescence; on fusing with 
NaHO, cooling, dissolving in water, faintly acidulating with 
HCl, and adding Fe,Cl,, a reddish purple is obtained. 


Lodoform. Yellow, insoluble in water, and characteristic odor ; warmed 
with alcoholic solution of KHO, and then mixed with starch 
paste and excess of HNOs, gives a blue. (May be detected in 
urine by adding alcohol and pouring upon phenol-potassium 
contained in a test tube, when a red color will cover the 
bottom of the tube ; soluble in alcohol.) 


Jalapin. Insoluble in water, but soluble in alcohol; soluble in 
alkalies, but not in dilute acids ; insoluble in turpentine. 
H,SO, dropped on a fragment turns it reddish, and on adding 
a few drops of water, so as to cause evolution of steam, the 
characteristic odor of jalap is observed. 


go 


QUALITATIVE ANALYSIS. 





Phenacetinum (phenacetin). Only slightly soluble in cold water, and 
not freely in chloroform. A hot solution gives a violet with 
chlorine water, fading to red; boiled with HCl and Fe,Cl, 
added gives a red; mixed with four drops of carbolic acid, and 
H,SO, added till the liquid boils, gives a purplish-brown color 
and odor of acetone; one grain boiled with 20 minims of HCl, 
and the liquid diluted with 10 volumes of water, cooled and 
filtered, gives a deep red with solution of chromic acid; does 
not give precipitate with bromine water, nor does it give the 
isonitrile test (d¢stinction from acetanilide). 


Phenazonum (antipyrin or phenyl-methyl-pyrozolone). Freely soluble 
both in water and chloroform; with NaNO, and diluted sul- 
phuric acid gives a green ; an aqueous solution with an equal 
volume of HNOs is yellow, passing to crimson on warming; 
Fe,Cl, gives a deep red, discharged by dilute acids (like an 
acetate) ; place some KNO, in a tube with a little water, then 
add excess of H,SO,, and fill the tube with solution of antipyrin, 
and get a green. 


LPicrotoxinum (picrotoxin). Slightly soluble in water, freely in chloro- 
form; soluble in solution of KHO, and the liquid reduces 
Fehling’s solution; H,SO, gives a saffron-yellow ; its solution 
is not precipitated by Meyer’s solution, by bismuth potassium 


iodide, PtCl,, or by tannic acid (showing that it is not an 
alkaloid). 


Podophyllin. Insoluble in water, but soluble in spirit; soluble in 
NH,HO, and precipitated therefrom by HCl; H,SO, on a 
fragment slightly colors it, and on adding a drop or two of 
water no characteristic odor is evolved. 


Resorcin. Freely soluble in water; Fe,Cl, added to an aqueous 
solution gives violet, discharged by NH,HO; Na,OCl, gives 
a violet, fading to yellow; NHsHO and CaOCl, gives a red 
violet, turning yellow. 


Resin. Insoluble in water, soluble in alcohol and in turpentine ; H,SO, 
on a fragment gives a strong red, and on adding a few drops 
of water, so as to cause evolution of steam, the characteristic 
odor is observed. 


Santonin. White when fresh, pale yellow when old ; nearly insoluble 
in water, soluble in alkali; added to a warm alcoholic solution 
of KHO gives a violet-red color, gradually fading away ; 
added to 1 c.c. of H,SO, and a few drops of Fe,Cl, and heated 
gives a red color changing to brown. (These well detect santonin 
in urine.) Heated on a porcelain dish and H,SO, added gives 
a purple. 

Sulphonal, Soluble in water and in chloroform ; fused with an equal 
weight of KCN the odor of mercaptan is evolved, and the 
residue dissolved in water, acidulated with HCl and Fe,Cl,added, 
a red color is produced; a solution mixed with 4 drops of 
carbolic acid, and. strong H,SO, added till the liquid boils, a 


- green color is obtained, turning darker on adding sulphurous 
acid. 


CEA Reb Rae 


QUALITATIVE DETECTION OF ALKALOIDS, GLUCOSIDES, 
AND CERTAIN ORGANIC BODIES USED IN MEDICINE, 
TOGETHER. .WITH A GENERAL SKETCH OF TOXICO- 
MOGICAL PROCEDURE. 


es 


DIVISION A. COURSE FOR THE DETECTION OF THE ALKALOIDS 
AND ALKALOID SALTS USED IN MEDICINE. 


Note.—Aconitine and atropine are omitted because they can only be really detected 
by experiments upon animals, which are now illegal except by special 
licence. Salicine, although not an alkaloid, is included for convenience, 
as it may be mixed with quinine. 


In this course not more than two definite ¢es¢s for each alkaloid are recorded, 
and for the remaining tests the reader is referred to the full table in Division D 
of this chapter. 


Step I. Heat on platinum foil. If the substance at once takes fire and 
burns away with a smoky flame and an odor of singed hair, it 
is probably an alkaloid. 


Step II. To a solution of the substance in water or dilute acid add :— 

(a) Mayer's solution (see index), which gives a precipitate with all 

official alkaloids (except caffeine), but no effect with antipyrin. 

(6) Solution of potassium bismuthous todtde,* which will give a 

precipitate with all official alkaloids, also with acetanilide and 
antipyrin. 


Step III. Put a piece of red litmus paper ona watch-glass, lay on to this 
a little of the substance, and moisten it with a few drops of 
strong rectified spirit. If, on standing for a short time, the paper 
is rendered blue, we are dealing with a free alkaloid ; if not, 
then it is an alkaloid salt, and in the latter case we shall have to 
search for the acid as well as the base. 
Note.—Acetates of alkaloids often become basic and consequently alkaline by 
keeping, so beware of this. | 
Step IV. To a fragment of the substance on a watch-glass (placed over 
white paper) add a drop of strong H,SO,, and stir :—a bright 
red=Salicine and a deep red=Veratrine. 
Confirm this latter by getting a yellow with HNOs; and a 
blood-red on warming with HCl. 
Note.—In each step any colors other than those herein recorded are to be disregarded. 
Many alkaloids give pale dirty pinks with H,SQ,. 
EEE eebdre se er Ne ee 
* Made by mixing 43 c.c of iguor bismutht with 9 grms. of KI and 9 c.c. of strong 
hydrochloric acid. 


Q2 


QUALITATIVE DETECTION OF ALKALOIDS, ETC. 





Step V. To the liquid in which H,SO, has given no distinct red add a 
small fragment of powdered ammonium molybdate, and stir. 
(2) oe pape | =Morphine or Apomorphine. 

Confirm by adding HNO; to another fragment, when pale 
red=morphine and fine purple=apomorphine. Further con- 
firm morphine with Fe,Cl, (blue) and with H,SO,+ Na,HAsO, 
(bluish-green). 

(2) Bright orange-red=Brucine. 

Confirm by testing another fragment with HNO, and getting 

a bright red, turned to violet on warming with SnCl,. 


(c) Bright greenish-blue= Codeine. 


Confirm by adding HNO; to another portion=pale evanes- 
cent yellow. 


(2) A yellowish-green= Physostigmine. 
Confirm by adding HNOs to another portion=strong gamboge 
yellow. Further confirm by getting a red with KHO, becoming 


blue on evaporating to dryness on the water bath, and dissolving 
in HCl to a dichroic solution. 


Step VI. Treat another fragment with a drop of H,SO, as before, then 
let another drop fall nearit. Into the second drop puta fragment 
of powdered potassium bichromate, let it digest a moment, and 
then stir the drops together. 


(2) Beautiful violet (evanescent)=Strychnine or Acetanilide, 

To distinguish between these we test original substance with 
HNO,, which gives no color with strychnine, but a dirty yellow 
with acetanilide, turned red by NH4HO. (Further confirmatory 
tests, see page 88.) 


(4) Emerald green after standing some time= Caffeine or Pilocarpine. 
Test another portion for caffeine by adding a crystal of KCIO, 
and a drop or two of HCl, evaporating to dryness, and getting 
a red residue, becoming purple with NH,HO. 
Note. —Do not decide too hurriedly about pilocarpine ; set the glass aside for half an 


hour, and then if the emerald green is guzte distinct and no cinchona alkaloid 
2s present you may conclude that pilocarpine is really there. 


(c) Dirty pale-yellowish pink =Cocaine. 


Note.—This test is not very good, but a minute drop of a dilute solution placed upon 
the tongue will cause tingling and numbness, and a strong solution will give 
a precipitate with (NH,),CO,, soluble in excess. (Aconitine, which also 
tingles the tongue, is not precipitated by (NH,),CO3.) 


Step VII. Dissolve some of the original in water (using a drop or two of 
acetic acid to help solution if necessary), then add chlorine water 
and a gradual excess of NH,HO. 

(a) A clear green solution=Quinine or Quinidine. 

(0) A white precipitate=Cinchonine or Cinchonidine. 

(c) A clear yellow=Phenazone (Antipyrin). (Confirm by nitrite 
test, see page go.) 

Note.—In presence of salicylate the ordinary tests for quinine fail, and in this case it 
is necessary to dissolve in dilute hydrochloric acid, shake up with ether to 


remove salicylic acid, and then draw off the watery solution from beneath 
the ether and test it for quinine. 


——— = 


ANALYSIS OF SCALE PREPARATIONS. | 93 





(2) To distinguish between quinine and quinidine. 

Dissolve in hot water with a drop of dilute H,SO, and cool, and 
if any crystals separate out they are probably sulphate of quinine 
and are rejected by filtration. (The proper proportion of 
water and alkaloid salt to start with is 1 of salt in about 25 of 
water. If you are dealing with a /vee alkaloid you must dissolve 
it in hot water with the smallest possible amount of dilute H,SO,.) 
Now add very carefully dilute NH,HO until the solution is as 
nearly neutral as possible without producing a permanent 
precipitate, cool perfectly, and add a few drops of saturated 
solution of Rochelle salts, and stir well or shake. This will 
precipitate quinine. If not, then add a little saturated solution 
(or a small crystal) of KI, and shake, which will precipitate 
quinidine, 

(0) To distinguish between cinchonine and cinchonidine. 

Dissolve in water, by aid of HCl if necessary, then cool and 
carefully make as nearly neutral as possible with very dilute 
NaHO (if necessary), and then add saturated solution of Rochelle 
salt and shake, when a precipitate=cinchonidine, If not that, 
then add NH,HO: white precipitate=cinchonine. 

Note.—The general principles to keep in mind as to the cinchona alkaloids are :— 

(1) That zz a neutral solution Rochelle salt precipitates quinine and cin- 
chonidine as tartrates, leaving the others in solution. (2) After filtration (if 
necessary) the addition of potassium iodide and a little spirit precipitates 
quinidine as iodide, leaving cinchonine and the amorphous alkaloids 
(quinoidine, etc.) in solution. (3) From this solution excess of ammonia 
precipitates both, and on shaking with ether the amorphous alkaloid 
passes into the ether and the cinchonine remains as a precipitate. (4) The 
separation of quinine and cinchonidine may be roughly performed by 
shaking up with ether, in the presence of a very slight excess of NH,HO, 
and then corking the tube and letting it stand in cold water for some hours, 
when cinchonidine, if present, deposits in crystals, and quinine remains in 
the ether. For this, the ether must be in very small quantity, just so as to 
form a distinctly visible layer. 

Step VIII. If we believe that we are dealing with an alkaloid salt we must 
now proceed to test for the acid. The acid radicals usually 
present in alkaloidal salts of commerce are, chloride, sulphate, 
acetate, phosphate, citrate, meconate, nitrate, and salicylate. 

The first step will be to dissolve a little of the alkaloid salt in 
very dilute HNOs, and test (1) for Cl by AgNOs3; (2) for SO, 
by BaCl, ; (3) for PO, by excess of ammonium molybdate and 
HNO. 

The next will be to dissolve in water only, and test with 
Fe,Cle for acetate or meconate (red) or salicylate (violet). 
(Acetate decolorised by boiling, meconate not so; also acetate 
gives no precipitate with Pb(C,H,O,),, and meconate does.) 

Lastly, we must test in the usual way for a citrate (but unless 
the base be caffeine, this is not likely), and also for a nitrate 
(especially with pilocarpine and strychnine). 


DIVISION B. QUALITATIVE ANALYSIS OF SCALE PREPARATIONS. 


These commonly contain— 


Metals Organic bases Acids 
Ammonium Quinine Tartaric 
Tron Cinchonine Citric 
Potassium Cinchonidine Pyrophosphoric (or hypo-) 
Strychnine Sulphuric. 


Beberine 


94 QUALITATIVE DETECTION OL ALKALOIDS, £IC. 


eS 


Step I. Heat a little to redness on platinum foil, and observe the 
following possible cases :— 


(a) If it entirely burns away we suspect Beberine sulphate. Test the 
original solution of the scale for sulphate by BaCl,, as usual ; 
and for beberine with KHO, getting a yellowish-white precipitate 
entirely dissolved by agitating the liquid with twice its volume 
of ether. This ether separated and evaporated to dryness 
leaves a yellow resinous-looking residue entirely insoluble in 
dilute HCl. If beberine sulphate be thus proved, go no farther. 


(2) An ash is left: (a) Put a small fragment of the ash upon a piece of 
red litmus paper, moisten it with a drop of water, and, if it 
turns the paper blue, suspect potassium; (b) Dissolve the 
remainder of the ash in nitric acid, dilute and test with excess 
of ammonium molybdate for phosphoric acid. 


Note.—If K be suspected, prove it by igniting some more of the scale, extracting the 
ash with very little boiling water, filtering, cooling, and adding PtCl,. 


Step II. Make a weak solution of the scale, acidulate it with a drop of 
HCl, and test for ferrous iron with K,le,Cy,,, and for ferric 
with K,FeCy, Also test another solution of the scale by 
adding excess of AgNO,, when a copious precipitate may form. 
Now add a drop of very dilute NH,HO till the precipitate jus¢ 
commences to dissolve, and heat, when reduction to black or a 
mirror=Tartrate. 


Step III. Make a fairly strong solution of the scale, add excess of NaHO, 
boil, and smell for ammonium. if neither phosphoric nor 
tartaric acid has been already found, filter out the precipitated 
ferric hydrate and use the filtrate for testing for acids as 
follows :— 


(a) Test a portion for citric acid exactly as directed in the organic acid 
course (page 80). 

(6) Test another portion by exactly neutralising with HNOs, and adding 
AgNOs, when a white precipitate= pyrophosphate, and the same 
turning black=hypophosphite. 

Of course this step is never to be taken unless an indication 
of P be got in the ash with molybdate in Step I. 


Step IV. Make a solution of a fair amount of the scale, add a drop or 
two of very dilute NH,HO, and then add some strong NH,HO. 
Scales with strychnine only will not show a precipitate ; with 
quinine they will give a precipitate with the dilute NH,HO. 
and this precipitate will dissolve in the strong ; with cinchonine 
or cinchonidine a precipitate (white) will remain even with 
strong NH,HO. 


Case (A). There is either no precipitate, or it dissolves in strong 
NH,HO :—Add some chloroform and shake up. Separate the 
chloroform by a pipette, and evaporate it to dryness in two 
portions on separate white dishes. Test the one residue for 
strychnine with H.SO, and K,Cr,O,, and the other for quinine 
with chlorine water and NH,HO. 

Case (B). The NH,HO causes a_ permanent white precipitate :— 
Filter out precipitate, and dissolve it off the filter with a little 
warm water containing a few drops of acetic acid. Boil the 


WE MOLION OF CARTAIN GLOCOSIDES, £ITC. 95 


solution down to a low bulk, cool, neutralise if necessary with 
very dilute NaHO, and:then add a few drops of saturated 
solution of Rochelle salts and shake, when a white precipitate 
=cinchonidine. If not that, then add NH,HO, when a white 
precipitate insoluble on shaking with ether=cinchonine. 


DIVISION C. QUALITATIVE DETECTION OF CERTAIN GLUCOSIDES, 
RESINS, AND ORGANIC BODIES, OTHER THAN ALKALOIDS. 


Step I. Heat on platinum foil, when the substance will char and burn 
away. 


Step II. Shake up with water acidulated with HCl, and to the resulting 
liquid add potassium bismuthous iodide, when xo precipitate 
must be produced. 


Note.—If a precipitate be formed, then the substance is to be looked for under 
Division A (page 91). 


Step ITI. Observe the color of the substance, try its solubility, first 
in cold water and then in cold chloroform, and apply the 
following :— 

Case (A). Substance zw/zfe difficultly soluble (or insoluble) in cold 
water, but readily in chloroform. Suspect and test for :— 


Elaterin . : : . page 8o. 
Picrotoxin : : : : re Ob; 
Santonin . : : : ars 
Sulphonal . : : é ss - bee 


Case (4). Substance which not readily soluble in cold water or cold 
chloroform. Suspect and test for :— 
Phenacetin : : : . page go. 
Saccharin (Gluside) . ; fai lie 


Case (C). Substance white (crystalline), and readily soluble in cold 
water; try for chloral hydrate (page 89), and for “soluble 
saccharin ” (see saccharin, page 89). 


Case (D). The substance is colored. Suspect and test for :— 


Aloin : 3 Sees? . page 89. 
Chrysarobin : : : ae 
Iodoform . ; Toe & 
Jalapin . : : : , ‘eee: 
Cholesterin (for Lanolin) . ; RA 
Podophyllin : ; : woo 
Resin ” : : ‘ are 
Santonin (may be pale yellow) . Sal 


DIVISION D. GENERAL SKETCH OF THE METHOD OF TESTING 
FOR POISONS IN MIXTURES. 


This course is only carried down to the best method of preliminary 
procedure for the zso/ation of the poison, all the individual tests to be after- 
wards applied having been already fully described in this or former chapters. 

Note.—Students desiring to study the subject more deeply are referred to any stan- 


dard work on toxicology, and especially to Dr. Leyda’s articles on detection 
of poisons in the Azalyst for 1890. 


96 QUALITATIVE DETECTION OF ALKALOIDS, ETC. 


een a re eee 


Step I. If the liquid be very strongly acid, and effervesces violently with 
NaHCoO,, test for poisonous acids, specially for Nitric and 

Oxalic. 
Note.—Oxalic acid is best separated from a mixture by precipitation with plumbic 
acetate, filtering, suspending the precipitate in water, and passing H,S.7 This 


removes the lead, and, after again filtering out the PbS, the liquid is 
evaporated to a suitable bulk and tested for oxalic acid. 


Step II, Acidulate with 4 of its bulk of HCl (filter, if necessary),!and 
apply Reinch’s test for As, Sb, and Hg. 


Step III. Burn to ash, dissolve this in HCl, and test by ordinary course 
for poisonous metals, especially Pb, Cu, and Zn. 


Step IV. If the original, either alone or when heated with dilute H,SO,, 
gives the odor of HCN or of carbolic acid, test specially for 
them. 


Step V. Uf the original has no odor of opium we proceed to apply Stas’s 
process for the detection of alkaloids as follows :— 

If the original be a solid, it is operated upon directly, but, 
if a fluid, it is first evaporated to dryness on a water bath. 
Add some strong alcohol and a small crystal of tartaric acid, 
boil, and filter. Evaporate the filtrate to dryness on the water 
bath, and take up with warm water slightly acidified with acetic 
acid, then cool and filter (if necessary), taking care that the 
liquid just remains acid. Now put this acid liquid into a 
separator (fig. 17), and shake it up with ether or benzine, and 
carefully separate the ether. (This ether may contain fat, 
certain bitter principles, and glucosides, and therefore, ina 
general investigation of a drug, it should not be rejected, 
but evaporated, and the residue examined.) Now make 
the liquid distinctly alkaline by the careful addition of 
Na2CO, or NaHO, and again shake up in the separator 
with chloroform, which will take up all the alkaloids 
except morphine. The chloroform is separated, evapo- 
rated at a very gentle heat, and the residue tested for 
alkaloids by the course given in Division A or by the 
table given in Division E of this chapter. Lastly, the ¥'8- 7. 
alkaline liquid is shaken up with amylic alcohol, which extracts 
morphine and leaves it upon evaporation. 

Note.—It is often better to get the alkaloids out from chloroform or amylic alcohol 
by shaking the separated solvent up with water acidulated with acetic acid 
or HCl, thus getting an aqueous solution and leaving any resinous matters 
in the chloroform. 


Step VI. When opium is suspected. Acidulate with acetic acid and filter, 
if necessary (any alcohol present being got rid of by boiling it 
off). Precipitate when cold with solution of plumbic acetate, 
filter, and preserve the precipitate (a) for examination for 
meconic acid and the filtrate (B) for morphine. 


(a) Precipitate (a) is suspended in water and treated with H,S till per- 
fectly decomposed; the PbS filtered out, and the filtrate, after 
evaporation to drive off H,S, tested for meconie acid. If this 
be found, it is held to be sufficient proof of presence of opium 
taken in connection with the odor of the original. 


TESTS FOR THE CHIEF ALKALOIDS. 07 


(6) Filtrate freed from Pb by H,S and filtering is evaporated to dryness 
with a slight excess of NaHCO; on a water bath. The residue 
will yield its morphine to alcohol, generally in a state suffi- 
ciently pure to evaporate a drop, and test. If not, then amylic 
alcohol must be used. 


DIVISION E. GENERAL RESUME OF THE TESTS FOR ALL THE 
CHIEF ALKALOIDS. 


The following tables are those given by Dragendorff in his ‘‘ Pflanzenanalyse. 
The author has carefully repeated these tests, and has found them to be fairly 
accurately described, except aconitine, for which the reactions given are not 
characteristic. Reference to such a list will rarely be necessary, the working 
by Division A already given being amply sufficient for all ordinary purposes. 

The following are the reagents used :— 


1. Pure strong sulphuric acid free from nitrous fumes. 
2. 200 parts of sulphuric acid with 1 part of nitric acid. 
3. ‘I gramme of sodium molybdate in to c.c. strong sulphuric acid 
(Frohde’s test). 
4. 1 part alkaloid mixed with 5 parts powdered white sugar, and then 
strong sulphuric acid dropped on. 
. Sulphuric acid and potassium bichromate used as already described 
in Division A. 
. Nitric acid (strong 1.3 sp. gr.) 
. Strongest fuming hydrochloric acid. . 
. Ordinary solution as neutral as possible. 
The reagents being generally added in turn to a fragment of the dry 
alkaloid, or to the residue left on evaporation of an alkaloidal solution. 


23 


com! OF On 





PART. IL. 
QUANTITATIVE ANALYSIS. 





CHAPTER VI. 
WEIGHING, MEAS URING, AND SPECIFIC GRAVITY. 


I. WEIGHING AND MEASURING. 


Ati bodies mutually attract each other. As the earth is the largest body 
within our atmosphere, it follows that its attraction is always greater than that 
of any surrounding matter. ‘The force thus developed is called the attraction 
of gravitation, and its exercise is the cause of weight. Weighing is performed 
by means of the well-known appliance called the balance. Figure) 18 
jllustrates a chemical balance of the modern short-beam type. H is the 
handle by which the balance is put into action, and R is the appliance for 


Ca 


TTI} 
A St fA 
Ss 
oY 












. 

















J 


Fig. 18. 


placing rider weights upon the eraduated beam, aided by weights made either 
according to the metrical or the English system, as follows :— 
(a) The Metrical system.—The metrical weights of precision above one 
gramme are in brass; and then we have °5, ‘2, ‘I, ‘I; and following them 
- ‘05, ‘02, ‘or, ‘or, all in platinum or aluminium foil. 
The quantities below ‘o1 (one centigramme) are weighed 
by a rider on the beam. The combination Of Seats 
. and 1 has been chosen because they have been found 
) to give the greatest number of possible combinations 
with the fewest weights. Figure 19 shows such a box 
_ Fig. 39. of metrical weights as usually employed in quantitative 
analysis. ‘The metrical system is founded upon the meéfre. The metre is 
multiplied and divided entirely by 10, thus :— 





WEIGHING AND MEASURING. 99 
Kilo-metre ‘ 1000° 
Hecto-metre. 100" 
Deca-metre . 10° 
Metre . 1° 
Deci-metre | 
Centi-metre . "OI 
Milli-metre . "OO! 


The metre taking the practical place of the English yard, the decimetre 


consequently takes the place of the foot, and the centimetre of the inch ; and 
just as weight is got in our system from the cubic inch, so it is got metrically 
from the cubic centimetre, only much more simply, because 1 cubic centimetre 
of distilled water, measured at 4° C. and 760 millimetres bar., weighs one 


gramme. ‘The gramme is multiplied and divided exactly as the metre, thus :— 

Kilo-gramme 1000° 

Hecto-gramme 100° 

Deca-gramme 10° 

Gramme - : . A 13 

Deci-gramme . ; : ; . "I 

Centi-gramme ‘OI 

Milli-gramme ‘OO! 


One kilogramme (1000 grammes) of water at the standard temperature and 
pressure measures one litre (or 1000 cubic centimetres), and we have therefore 
the following simple relation of weights and measures of water :— 


Weight. Measure. 
1000 grammes 1 litre or 1000 cubic centimetres. 
100 ve I deci-litreor 100 4, 455 
10 t I centi-litre or 10 ,, 45, 
I gramme I milli-litre or 1 cubic centimetre. 


So we see that using water at 4° C., a gramme by weight and a cubic centi- 
metre by measure amount to the same thing; as likewise do a kilogramme 
by weight and a cubic decimetre (or litre) by measure. The relation between 
the two systems is easily calculated from the following standards :— 


1 Gramme = 15'432 grains, troy or avoirdupois. 

1 Kilogramme = 15,432 grains = 2'205 lbs. avoirdupois = 2°68 Ibs. troy. 
1 Litre = 2°11 pints = 38°81 fluid ounces wine measure. 

1 Metre = 39°37 inches. 


So that 1 decimetre is, as nearly as possible, 4 inches ; and 1 decilitre, a trifle 
under 4 fluid ounces. 

(6) The English system.—In weights of precision, any amount above Io 
grains is usually represented by a series of small brass cylinders, from 10 to 
tooo grains; then follow 6, 3, 3, 2; and 1 grain in platinum wire, and 
afterwards °6, °3, °3, ‘2, and ‘1 of a grain in platinum, or, more frequently, 
in aluminium wire. Quantities of less than 5 grain are weighed by a small 
rider of gold wire placed on the beam of the balance. The foundation of 
the English system is the inch. One cubic inch of distilled water, measured 
at 60° F. and 30 inches barometrical pressure, weighs 252°45 grains, Or 
2524 grains nearly. ‘There are 437°5 grains in an ounce, and 16 ounces 
(or 700 grains) in a pound. Measure of capacity is obtained by weighing 
out to Ibs. of water at 60° F. and 30 inches bar., when the whole measures 
one gallon. The gallon is in turn divided into 8 pints ( = 20 ounces, or 8750 
grains of water, per pint); the pint into 20 fluid ounces ( = 437°5 grains 
of water per fluid ounce) ; the fluid ounce is divided into 8 fluid drachms 
(= 54°68 grains of water per fluid drachm); and, lastly, the fluid drachm 
is divided into 60 minims ( =‘gr grain of water in each minim). 


100 WEIGHING, MEASURING, AND SPECIFIC GRAVITY. 


II. SPECIFIC GRAVITY 
may be generally explained to be the weight of anything as compared 
with that of an equal volume of something else taken as a standard. For 
liquids and solids the standard is distilled water at a temperature of 60°. An 
acquaintance with the various cases which may occur in the taking of specific 
gravity is of great importance, as it forms an exceedingly ready method of 
testing the purity and strength of many substances. A knowledge of the 
specific gravity of the various bodies also enables the chemist to tell at once 
what any given volume of a liquid ought to weigh, or conversely, what size of 
vessel will be required to contain any given weight. The following are the 
chief varieties of cases which may occur in taking :— 


(A) Specific Gravity of Liquids. 

Case 1. To take the specific gravity of a fluid—A small bottle of thin 
glass is procured, and counterpoised upon a balance. It is then filled with 
distilled water at 15°5° C. (60° F.), and the weight of the water thus introduced 
noted. The bottle, having been emptied and dried, is filled with the liquid 
to be tested, also at 15°5° C. (60° F.), and the whole is again weighed. By 
this means, having ascertained the weight of equal bulks of water and fluid, it 
only remains to divide the weight of the fluid by the weight of the water, and 
the quotient will be the specific gravity required. ‘To make the calculation 
clear, observe the following examples :— 

A counterpoised kottle filled with distilled water weighs 100 grammes: the same bottle 
filled with sulphuric acid weighs 184°3 grammes, then :— 

owe —= 1'843, the specific gravity of the acid. 


Again, the same bottle, carefully washed, and filled with rectified spirit, weighs 83°38 
grammes, then :— 


oe = ‘838, the specific gravity of rectified spirit. 

In practice, bottles are sold with perforated stoppers, which, when entirely 
filled with the liquid, and the stopper dropped in, so that no bubbles of air 
are allowed to remain between the stopper and the liquid, exactly hold a 
given weight of water. A counterpoising weight for the empty bottle is also 
provided ; so that there is nothing further to be done but simply to place 
the counterpoise in one scale, and the bottle, filled with the liquid under 
examination, in the other; and having ascertained the weight, to divide by 
the known weight of water for which the bottle was 
constructed. Fig. 20 shows an ordinary specific gravity 
bottle. Fig. 21 shows a specific gravity bottle the 
stopper of which is a thermometer, thus enabling us to 
observe the exact temperature of the liquid at the 
moment of weighing. 

Casr 2. To take the specific gravity of a liquid by 
means of the hydrometer.—The hydrometer depends 
for its action on the theorem of Archimedes. Ifa solid 
body be immersed in a liquid specifically heavier than 
itself, it continues to sink until it has displaced a bulk 
of fluid equal to its own weight, and then it becomes 
stationary. Suppose an elongated body with a weight 
a at its base to cause it to float upright, which has a 

Elees ames ee specific weight exactly half that of water, be immersed 
in that fluid, it will sink to exactly half its length, because its whole weight is 
counterpoised by a bulk of fluid equal to half its size. Hydrometers are long 
narrow glass or metal tubes with a bulb near the bottom filled with air, and 
another smaller bulb beneath containing a sufficient quantity of mercury to 




















SPECIFIC GRAVITY. IO! 


a I ————————————————————E ne 


weight it and cause it to float upright. ‘There are two kinds of hydrometers : 
(1) for fluids heavier than water, and (2) for fluids lighter than water. The 
graduation of the former is performed by immersing the instrument in water 
and introducing such a quantity of mercury as will cause it to sink, so that 
only about one inch remains unsubmerged, and marking this point 1. The 
instrument is then plunged successively into several liquids heavier than 
water, the specific gravities of which are known, and the points to which 
it rises are marked and numbered. By this means a scale can be made 
between those points, indicating any gravity from 1 upwards. In hydro- 
meters for fluids lighter than water, the first sinking in that liquid is 
continued by weighing until only the upper bulb is immersed; and this 
point having been marked 1, the instrument is placed successively in known 
fluids lighter than water, the points to which it sinks marked, and by this 
means a whole scale is obtained. The method of using the 
hydrometer is readily seen from the illustration (fig. 22), in which 
A is the hydrometer, and B is a thermometer also placed in the 
liquid to show the temperature. Most hydrometers being made to 
indicate specific gravity at 15°5° C. (60° F.), it follows that the liquid 
must either be first brought to that temperature before using the 
instrument, or else the temperature employed must be noted, and a 
calculation made, based upon the coefficient of expansion of the 
liquid in question. 

Sykes’s hydrometer is used in England by the officers of excise 
to indicate the strength of spirituous liquors, and thus facilitate the 
collection of the revenue. It is a short brass instrument with the stem 
graduated from o to ro, and a series of nine weights to place beneath the 
bulb. By observing (1) the temperature, (2) the weight put on, and (3) the 
point to which it sinks on the stem, and referring to a book of tables which is 
sold with the hydrometer, the strength of the spirit is ascertained. Another 
modification of the instrument is,found in Zwaddell’s hydrometer, which is 
used in chemical works for testing the density of liquids having a greater 
specific gravity than water. It is so graduated that the reading of any indi- 
cated degree, multiplied by 5 and added to 1000, gives the specific gravity 
as compared with water. Specific gravity beads form the only other variation 
of the hydrometric idea. ‘These ‘are small loaded bulbs of known specific 
gravities, which are thrown into the liquid to be tested, when the number 
marked upon the bead, which just floats underneath the surface and shows 
no tendency to sink or rise, gives the specific gravity required. Hydrometers 
in any form must in accuracy rank considerably beneath that of the specific 
gravity bottle ; but in commercial operations, where an approximation only to 
correctness is required, these little instruments are invaluable. 

CasE 3. To take the specific gravity of a liquid by weighing a solid 
body in it.—Take the weight of a glass stopper, or other suitable plummet, 
by suspending it from the hook provided for the purpose in all balances of 
modern type (see fig. 12, page 6). Put a wooden stool (also provided with 
all modern balances) over the pan, and upon this place a beaker containing 
distilled water at 15°5° C. (60° F). Let the plummet hang beneath the surface of 
the water and again weigh, and then empty out the water, substitute the fluid 
(also at 15°5° C. (60° F.), immerse the plummet as before, and once more weigh. 
By deducting respectively the weights in water and in fluid from the weight in 
air, we get the loss of weight sustained by the plummet in each case. It is 
evident that the lighter the liquid, the more the plummet will weigh ; therefore 
we divide the loss of weight in the fluid by the loss of weight in water, which will 
give the specific gravity of the liquid. This rule is now practically applied in 
all modern laboratories by means of the Westphal balance (fig. 2 3). By this 





102 WEIGHING, MEASURING, AND SPECIFIC GRAVITY. 





a small thermometer (a), adjusted to a counterbalancing weight (8), is placed 
in the liquid, and the loss of weight is restored by little rider weights placed 
on the beam, which are so contrived as to readily indicate the specific gravity 
without calculation. 


(B) Specific Gravity of Solids. 


Case 1. To take the specific gravity of a solid body in mass which is 
insoluble in and heavier than water.—The method 
by which this process is conducted was suggested by 
a theorem attributed to Archimedes, which may be 
n thus expressed :—A solid on being immersed in a 
* liquid is buoyed up in proportion to the weight of 
Jt the fluid which it displaces, and the weight it thus 
JU apparently loses is equal to that of its own bulk of 
d the liquid. A piece of the solid substance to be tested 
is weighed, and is suspended by means of a fine 
thread from one arm of a balance so that it dips 
under the surface of a vessel containing distilled water 
Higa 23- at 15°5° C. (60° F.), when its weight is again noted. 
Its weight in water is deducted from its weight in air, and the weight in air 
is divided by the difference so obtained, which gives the specific gravity. 


B 





EXAMPLE. 
A piece of marble weighs : ; : , 30 grammes. 
Immersed in distilled water . : : ; 18°SQ "55 
Difference in weight . : : is @ ae 


By dividing 30 by 11°11 we obtain the quotient 2°7, which is the specific gravity of the 
marble. The practical arrangement has been already described above (Lzguids, Case 3). 


Cask 2. To arrive at the specific gravity of a powder which is insoluble 
in and heavier than water.—Weigh a portion of the powder in air, then 
introduce it into a counterpoised specific gravity bottle constructed to hold 
a known weight of water. Let the bottle be carefully filled with distilled 
water, gently agitating to insure that no minute bubbles of air shall remain 
attached to the particles of powder ; then weigh the whole. From the weight 
of the powder in air, Z/ws the known weight of water which the bottle should 
contain, deduct the weight obtained in the second operation, and divide the 
original weight of the powder by this difference. 

EXAMPLE.—2 grammes of a powder are weighed out, and poured into a counterpoised 


specific gravity bottle, constructed to hold 100 grammes of water. The bottle thus charged 
is found to weigh I01°'2 grammes; then, 


2 grammes + 100 grammes = 102 grammes. 
Weight of the bottle when charged 


with powder and water : é heey 


Difference : : : : 8 s. 


heey 2 grammes divided by ‘8 gramme will give 2°5 as the specific gravity of the 
powder. 


CasE 3. To take the specific gravity of a substance in mass, insoluble in 
but lighter than water.—The difficulty met with in this case consists in the 
impossibility of weighing such a substance alone in water, because it floats on 
the surface of that liquid. It therefore becomes necessary to attach a piece 
of lead sufficiently heavy to sink it, and thus a complication is introduced. 
The light substance is first weighed in air in the ordinary manner, and is then 
attached to a sinker, and suspended from one arm of a balance under the 
surface of distilled water, when the combined weight of both is ascertained. 


SPECIEIC GRAVITY. 103 


eee EnTIETEEIEIEINIERERERE EERE 


The light body is now detached, and the weight of the sinker alone in water 
noted. By these means we obtain the following data :— 


i. The weight of the light body in air. 
ii. The weight of the sinker in water. 
iii, The weight conjointly of the light body and sinker in water. 


We then deduct the weight of both in water from the weight of the sinker in 
water ; add the weight of the light substance in air ; and divide the weight of 
the light body in air by the product so obtained. 


EXAMPLE.—A light substance weighs 12 grammes in air; being attached to a piece of lead 
and weighed in distilled water the united weight amounts to 4 grammes, while the weight of 
the lead alone in water shows 5 grammes. Then :— 


Weight of lead in water : : : 5 grammes. 
Weight of both in water ; i : 4 re 
Difference . - : 3 : I gramme. 
Add weight of light body in air . . 12 grammes. 
Sum.” + - : ; : . BASS “s 


Dividing 12, the weight in air, by 13 obtained as above, we arrive at the decimal fraction 
‘923 as the specific gravity of the light substance tested. 


Casz 4. To obtain the specific gravity of a substance soluble in water.— 
Proceed exactly in the same manner as in Case 2 or 3, according as the body 
is in mass or in powder ; but instead of water, use oil of turpentine or some 
other liquid in which the solid is insoluble. Having obtained the specific 
gravity of the substance by calculating just as if water had been used, multiply 
the result by the known specific gravity of the oil of turpentine or other fluid 
employed. 

ExAMPLe.—A lump of sugar weighing Io grammes was found to weigh when immersed in 
oil of turpentine 4°562 grammes. Then :— 





The weight of the sugar in air was . : . 10 grammes. 
» ” oil of turpentine . 4°562 ,, 
Difference . 5°438 5, 


Dividing 10 grammes by 5°438 grammes yields 1°84 as the specific gravity, as if water had 
been used; and by multiplying this result by ‘87, the specific gravity of oil of turpentine, we 
obtain 1°6 as the actual specific gravity of the sample of sugar operated on. 


Having thus considered in detail the various complications which may arise 
in taking the specific gravity of liquids and solids, it only remains to point out 
how the foregoing may be rendered subservient to commercial purposes. 


(C) Practical Applications of Specific Gravity of Solids and Liquids. 


Casr 1. The specific gravity of a body being known, it is desired to as- 
certain the weight of any given volume of the substance. Find the weight 
of the given bulk considered as water, and multiply this amount by the 
specific gravity. 

EXAMPLE i.—What would be the weight of a fluid ounce of oil of vitriol? We know that 
a fluid ounce of distilled water weighs 455°7 grains, and the specific gravity of oil of vitriol is 
1°843 ; so, if we multiply the former figures by the latter, we obtain 838°75 grains, which is 
the weight of a fluid ounce of this acid. 

EXAMPLE ii—How much should a litre of chloroform weigh? The weight of a litre of 
water is 1000 grammes ; and by multiplying 1000 by 1°49, the specific gravity of the chloroform, 
we obtain 1490 grammes, as an answer to the question. 

EXAMPLE iii.—How much should a fluid ounce of pure ether weigh? The specific gravity 
is °72, and a fluid ounce of distilled water weighs 455°7 grains ; multiplying the one number by 
the other gives 328°1 grains. 


104 WEIGHING, MEASURING, AND SPECIFIC GRAVITY. 





Case 2. Given the weight of any known bulk of a liquid, to find its 
specific gravity. Divide the weight by that of the given bulk considered as 
distilled water. 

EXAMPLE.—A pint of alcohol weighs 5978°78 grains ;—is it dilute alcohol or alcohol 
U.S.P.? By dividing this weight by 7291°2 grains, the ascertained weight of a pint of 
distilled water, we obtain as an answer ‘820. We know, therefore, that the spirit thus tested 
must have been alcohol of U.S.P. strength (91 per cent.). 


Case 3. To find the amount of solid matter, in grammes, present in 100 c.c. 
of a solution of given specific gravity. So far as any ordinary rule can 
be laid down, especially with regard to saccharine liquids, for which this 
calculation is generally used, we multiply the gravity by rooo, and then, having 
deducted 1000 from the product, we divide by 3°85. 


EXAMPLE.—A saccharine solution has a gravity of 10114: how much solid matter in 
grammes does it contain in each c.c. ? 


I‘OII4 X 1000 = IOII'4—1000 = I1'4.", —5- = 2°961 grammes per I00 C.c, 


II'4 
3°35 


(D) Specific Gravity of Gases. 


Taking the density of gases and vapors involves many more complicated 
considerations than are required in the methods applicable to the specific 
gravity of liquids and solids. The standard adopted for such bodies is 
hydrogen, measured at a temperature of o° C. and a barometrical pressure 
of 760 millimetres. 

When taking the specific gravity of liquids or solids, it is easy to obtain the 
water or other fluid required at the exact temperature necessary, by the use of 
cooling or heating appliances. With a gas we need exercise no such manipu- 
lation, because the coefficient of expansion of all gases and vapors is alike and 
well ascertained. ‘The measurement of gases is therefore conducted without 
any attempt to modify these conditions; but the indications of the thermo- 
meter and barometer being carefully noted at the time of the experiment, a 
simple series of calculations enables us to ascertain how much the volume of 
gas would have measured had the test been conducted at a standard of tem- 
‘perature and pressure. ‘The following are specimens of such calculations :— 

1. Correction of the volume of gases for temperature.—This calculation 
is based upon Charles’s law, viz.: gases expand or contract one two-hundred- 
and-seventy-third (5+) part of their volume for each degree of temperature, 
Centigrade, through which their heat has been respectively raised or lowered. 
Therefore :—As 273 plus the temperature at the time of measurement is to 
273 plus the required temperature, so is the volume of the gas at the period of 
measurement to the required volume. 


For example :—The volume of a gas at 15° C. was 100 cubic centimetres: what would it 
be at the standard temperature of 0° C.? Then,— 


As. 273 273 
15 oO 
288 [ie SC 29s0 or PaO, 


which gives, as an answer, 94°795 cubic centimetres, the volume of the gas at standard 
temperature. 


2. Correction of the volume of gases for pressure.—This calculation is 
based upon Boyle’s law, viz.: gases expand or contract in volume in inverse 
proportion to the increase or diminution of the pressure,—that is to say, the 
greater the pressure the less the volume of gas, and the less the pressure the 
greater the volume of the gas. 


For example :—At the moment of measuring 100 cubic centimetres of a gas, the barometer 
stood at 752 millimetres: what would the volume of the gas be at the standard pressure of 


VAPOR DENSITY. 105 





760 millimetres? Applying the rule of inverse proportion, we have :—As the required pressure 
is to the observed pressure, so is the observed volume to the required volume : then 


TE Peer 9 G2; 1 te TOO, 
which gives, as an answer, 98°95, the volume of the gas at standard pressure, 


The manner in which the specific gravity of a permanent gas was formerly 
obtained was by exhausting a thin glass globe by means of the air pump and 
weighing it; then filling it with air at known temperature and pressure, and 
weighing ; and lastly, pumping out the air, filling the globe with the gas at a 
similar temperature and pressure, and again weighing. After deducting the 
weight of the empty globe from each of the two latter weights, the weight of 
the gas was divided by that of the air. 

Now, however, in modern laboratories all that is practically done away with, 
and the standard taken for the density of gases and vapors is hydrogen ; 
- because (1) it is the lightest known gas, and (2) we know the weight of any 
given volume of it without the necessity of weighing each time. ‘Therefore 
to take the density of a gas or vapor we weigh a given number of cubic 
centimétres of the gas, noting the temperature and pressure at the moment of 
weighing, and having corrected the volume so obtained to o° C. and 760 m.m. 
bar., we divide this by the weight of the same number of c.c. of hydrogen. A 
litre of hydrogen at o° C. and 760 m.m. bar. weighs ‘0896 gramme; therefore 
each c.c. of H will weigh ‘oo00896 gramme. 


(Z) Vapor Density. 


_ After finding the percentage composition of organic bodies, and from that 
calculating an empirical formula (which is done by dividing the percentage 
of each element by its own atomic weight, then, taking the lowest of these 
answers as unity, dividing all the others by it and expressing the mutual 
ratios in the simplest full numbers), it is often necessary to prove whether the 
sum of such formula is the true molecular weight. Upon the theory that all 
molecules occupy a space double that of an atom of hydrogen, we can prove 
our case by taking the density of a volume of the substance in 
vapor (if volatile) as regards hydrogen, and then this vapor den- 
sity X 2 =the true molecular weight. ‘This research acts as a check 
upon our formula obtained by analysis, and may or may not lead to 
our having to double it. 

(a) V. Meyer's Method.—This is the simplest and most rapid pro- 
cess. The apparatus used is illustrated in fig. 24. The inner tube (a) is 
closed with a cork and arranged so that its bent delivery tube just dips 
under the surface of mercury contained in a trough. Any suitable 
liquid, which boils at a constant temperature, is placed in the outer 
tube (B), together with a thermometer, and heat being applied so as 
to boil the fluid, the air in the inner tube expands and passes off 
through the mercury. When bubbles of air cease to pass (showing 
that the air in the tube has been fully expanded to its proper volume 
at the given temperature), some water is poured upon the surface of 
the mercury, and a graduated “gas collecting tube” is filled with 
water and inverted over the delivery tube. A known weight of the substance 
is then introduced into the inner tube (a) by rapidly raising the cork, dropping 
the substance in, and instantly closing again. The vapor produced now 
displaces an equivalent volume of air, which passes into the measuring tube. 
When action ceases, the cork is opened to prevent back suction, and the air in 
the tube is measured, noting temperature and pressure. This volume in cen- 
timetres corrected to N.T.P., and multiplied by ‘ooo0896, gives the weight 
of a volume of hydrogen equal to that of the vapor, and then by dividing the 











106 WEIGHING, MEASURING, AND SPECIFIC GRAVITY. 


weight of the substance taken by such weight we obtain the vapor density. 
The coefficient of expansion of all gases being equal, it is quite the same 
thing whether we measure an actual volume of vapor at a given temperature, 
or that of an equivalent volume of air displaced at the same temperature. 
Such a minute quantity of the substance must be taken as shall not, when in 
vapor, more than displace the air contained in the inner tube of the apparatus 
(which should hold about roo c.c.), otherwise the whole process manifestly fails. 

(2) Dumas’ Process.—A thin, clean, dry glass globe, about three inches in 
diameter, is employed. Its neck having been drawn out to a fine tube in the 
blowpipe flame, it is weighed, and the temperature and pressure noted. By 
gently heating the bulb and dipping the open end into the volatile liquid, a 
suitable quantity is drawn into the globe by the contraction of the air. 
Attaching a handle by means of wire, the sphere is plunged into an oil bath 
urnished with a thermometer, and is then heated somewhat above its volati- 
lising point. When all vapor has ceased to issue from the globe, the orifice 
is hermetically sealed, and the temperature and pressure again noted. The 
apparatus is allowed to cool, separated from the handle, cleansed, weighed, 
and the weight noted. ‘The last step is to break off a fragment of the neck 
beneath the surface of a sufficiency of mercury, when, should the experiment 
have been carefully performed, the liquid enters the globe, completely filling 
it, and the capacity is ascertained by emptying its contents into a graduated 


glass measure. Supposing the experiment to have been perfectly successful, 
we have the following five data :— 


1. Weight of globe filled with air. 

2. Temperature and pressure at the time of weighing. 
3. Weight of globe A/us vapor. 

4. Temperature and pressure at sealing. 

5- Capacity of the globe. 


Proceeding from these data, the first point is to find the actual weight of 
the globe. This is done by calculating the capacity of the globe from the 
temperature and pressure at the time of weighing to 0° C. and 760 m.m. bar., 
and then multiplying the true volume thus found by ‘oor295, which is the 
weight of a cubic centimetre of air (1 litre at o° C. and 760 m.m. bar. = 1'295 
gramme). Having thus obtained the weight of the air, it is deducted from 
the weight of globe and air, and the difference gives the true weight of the 
globe ; and by deducting this latter from the weight of the globe A/ws vapor, 
we obtain the actual weight of the vapor. But as this weight is that of the 
volume of vapor at the temperature and pressure at the moment of sealing, 
it must be corrected to standard temperature and pressure, and the weight of 
an equal volume of hydrogen ascertained. To do this, the capacity of the 
globe is once more put down, and reduced from the temperature and pressure 
at sealing to o° C. and 760 m.m. bar., and the resulting volume is multiplied 
by ‘0000896, which is the weight of 1 cubic centimetre of hydrogen. The 
product, which gives the actual weight of an equivalent volume of hydrogen, 


is then taken, and divided into the weight of the vapor already found, and 
the answer is the density. 


CTX eet eV Ula 
VOLUMETRIC QUANTITATIVE ANALYSIS. 


—_—— 


I. INTRODUCTORY REMARKS. 


VOLUMETRIC analysis is that in which the quantity of any reagent required to 
perform a given reaction is ascertained, and the amount of the substance acted 
upon is found by calculation. The process of adding the reagent from a 
graduated measure is called Titration. 


(A) Volumetric or standard solution is a solution of definite strength 
made by dissolving a given weight of a reagent in grammes in a definite 
volume of water in cubic centimetres (or in grains and fluid grains). Such 
solutions are usually made by dissolving the combining weight of a reagent 
in grammes (or some decimal fraction of such weight) in 1000 c.c. (one 
litre) of water. The following abbreviations are used to express the strength 
of standard solutions :— 


N=a normal solution having 1 combining weight in grammes per litre (7.2. the 
weight of the body that is equivalent to 1 gramme of hydrogen). 


oe deci-normal solution having 31, combining weight in grammes per litre. 


ee wet is 7 
eck viginti-normal rf ao ” 9 9 ” 


(B) An indicator is a substance added to enable us to ascertain, by a 
change of color (or other equally marked effect), the exact point at which a 
given reaction is complete. i 

The principal indicators employed are as follows : — 

(a) Solution of litmus, which turns red with acids and blue with 
alkalies. 

4 (2) Alcoholic solution of phenol-phthalein, which is colorless with acids 
and red with alkalies, but is not accurate when alkaline salts of 
ammonium or phosphoric acid are present. 

(c) Methyl orange in alcohol, which is red with acids and yellow with 
alkalies, and may be used for the titration of alkaline carbonates 
because it is not affected by carbonic acid. 

(d) Rosolic acid in diluted alcohol, which is yellow with acids and red 
with alkalies, and may be used when alkaline salts of ammonium 
or phosphoric acid are present. 


Note.—Elderberry juice, preserved by } its volume of alcohol, has been recently re- 
commended by Dr. Hamilton as being the most universally useful indicator for 
alkalies, being green with them and red with acids. It may be used even with 
ammonia, and is in favor in the U.S.A. 


(e) Starch mucilage, which turns blue in presence of free iodine. 
(f) Solution of potassium chromate, which gives a red with AgNOs, but 


108 VOLUMETRIC QUANTITATIVE ANALYSTS. 





not until any halogen present has entirely combined with the 
silver. 

(¢) Solution of potassium ferricyanide, which ceases to give a blue color 
when any iron present has been fully raised to the ferric state. 


(C) General modus operandi. A known weight of the substance to be 
analysed is accurately weighed, and having been dissolved or diluted with 
water (if necessary), the solution is placed in a flask, the indicator is added, 
and the standard solution of the reagent is dropped in until the desired effect 
is attained. 

The volume of the standard solution used is then noted ; and its strength 
per 1000 c.c. being known, the actual amount of solid reagent that has been 
really added is easily found and calculated, by means of the equation for the 
action in question, to the amount of the substance under analysis it represents, 
as follows :— 

Suppose, for example, we desire to ascertain the strength of a sample of 
caustic soda, and that we have weighed out 1 gramme, dissolved it in water, 
added litmus solution, and found that it required 24 c.c. of standard solution 
of oxalic acid (63 grammes per 1000 C.c.) to just cause the color to change 
from blue to violet red (z.e. to neutralise it). Now, by the equation :— 


H.C,O, . 2H,O + 2NaHO = Na,C,0, + 4H,O 
ae ere 


_——_ 
fags 209 
63 40 = grammes of NaHO, equivalent to 1000 c.c. of oxalic 
acid solution (its strength being 63 grammes per 
1000 C.c.), . 


Knowing this, we now ascertain how much NaHO is represented by the 
24 c.c. of acid used; thus :— 


ee = ‘96 gramme of real NaHO present in the 1 gramme of caustic soda 


weighed out for analysis. 





Then, if the results are to be expressed in percentage, we multiply the 
amount of the real article found by 100 and divide by the quantity weighed 
out for analysis, thus :— 


*96 X 100 


: = 96 per cent., strength. 


Expressing the above calculations in rules to commit to memory, we have 
the following four steps :— | 
I. Write out the equation and reduce the first side of it to figures in 
molecular weights. 
II. Cancel these weights down to equivalent weights corresponding to 
the indicated strength of the standard solution used (z¢. if 


N aj 
ae divide by 1o, if ‘ divide by 20, etc.), thus obtaining the 


equivalent of the substance under analysis to 1000 c.c. of the 
standard solution. 

III. Multiply this equivalent by the number of centimetres of standard 
solution used and divide by 1000. 

IV. If percentage be required, multiply the last result by 100 and divide 
by the weight of substance taken for analysis. 


Note.—It must be remembered that all waters of crystallisation must always be 
added to each substance containing them, in writing the equation for volumetric 
calculations. 


—“_— 


INTRODUCTORY REMARKS. 109 





(D) The apparatus specially employed in volumetric analysis. 

1. Zhe measuring flask, so constructed as to hold a definite amount of 
fluid (say 1000 or 100 ¢.c.) when filled up to the mark on the 
neck (fig. 25). 

2. The test mixer, a cylindrical vessel, to hold 1 litre of fluid graduated 
in measures of 10 c.c. each (fig. 26). 

3. The burette, a graduated tube, usually containing 100 C.C.! and 
graduated in divisions of 1 c.c., for containing and delivering 
the standard solution. This is fitted with a clamp or stopcock 
at the bottom, which, when pressed or turned, allows the 
contained liquid to run out at any regulated speed desired. It 
should also be furnished with an appliance called ‘“ Erdmann’s 
float,” which enables us to read the quantity of fluid delivered 
more accurately. (Fig. 27 shows two burettes in their stand as 
usually employed.) 

4. The pipette is‘an instrument graduated to deliver a fixed volume of 
liquid (say 10, 20, 50, or 100 c.c.). Fig. 28 shows ayset of such 
instruments arranged in a convenient stand. 


£2 








sU 


°o 


AUCOOVAUIGH UCT OURO UND UOMO FLU) QU ua 2 





Fig. 25. Fig. 26. 


(Z) Weighing Operation. The student should have a tared watch-glass 
for weighing out solids and a small stoppered bottle for weighing volatile 
liquids. By carefully keeping these much trouble is saved. 

(1) Zo weigh a solid. Place the tared glass on the scale, and put on 
it what is judged to be a sufficient quantity of the article to be 
weighed, then weigh the whole and note the weight thus :— 

Glass + substance . : : , . 5°632 grammes. 
Known tare of glass . , r 7 e532 3 


PP Paso sre 

(2) Zo weigh a volatile liquid. Fill the small stoppered bottle with the 
liquid and weigh ; pour out what is judged to be sufficient into 
the flask containing the indicator and some water, replace the 
stopper and again weigh, noting each weight at the time thus :— 


Total weight of bottle + fluid. : . 20°982 grammes. 
Weight of bottle+ fluid after pouring out . I 5°482 Hs 


Weight taken for analysis . : ; 





Weight of fluid taken ; : : 57500 2 


IIo VOLUMETRIC QUANTITATIVE ANALYSIS. 





Note.—It is most important always to take the weights directly down in a note-book 
from the balance, and to cultivate the habit of always replacing the weights 
in their proper holes in the weight box when finished. ‘This enables us to 
have a double check, (1) from the weights in the pans, and (2) from looking 
at the empty holes in the weight box. In weighing, brass weights are used 
from 50 to I gramme; flat platinum weights from ‘5 to ‘oI gramme, and 
the rider on the beam is used for milligrammes (z.e. ‘009 to ‘oo1). Before 
weighing, see that all the weights are in their right places in the box. At 
the conclusion of the weighing, read off the weights and put them down in 
a note-book, and then check that reading by putting them back into the 
box, looking, as you do so, at the note already made. Always close the 
case of the balance before using the rider, so as to prevent currents of air 
affecting the weight. 

Having thus given a general idea of the mode of working, we now commence 


to practise with the chief standard solutions as follows. 


Il. STANDARD SOLUTION OF OXALIC ACID. 
Strength :-—equivalent N=63 grammes per 1000 ¢.¢. 
(A) Preparation, 


This is made by powdering some pure oxalic acid, pressing it between the 
folds of blotting-paper (to remove any chance moisture), and weighing out 
exactly 63 grammes in a tared beaker. The powder is then washed out with 
distilled water from the beaker into the litre measuring flask, which is nearly 
filled with water and slightly warmed to aid solution. When all is dissolved, 
more water is poured in till the solution arrives at the mark in the neck of 
the flask, and finally the whole is cooled down to 60° F., and is once more 
exactly made up to the line with water. 

This solution may then be used for the following purposes in the manner 
described under each case. 

Check.—To check the strength of the standard oxalic acid itself. Take 
some pure NaHCOs, and ignite it ina crucible for 15 minutes at a red heat, 
cool and weigh off 2°65 grammes of the resulting Na,COs, and this should take 
exactly so c.c. of acid if correct. The process is described below at (C). 


(2) Estimation of Alkaline Hydrates. 


By weighing out a definite quantity of the substance, diluting with, or 
dissolving in, water in a flask, adding a few drops of a suitable indicator, and 
dropping in the standard acid from a burette until the last drop added just 
causes the color to change; the flask being agitated after each addition of 
the acid. In this way we should examine :— 


(a) Liquor ammonia fort. and liquor ammonia. 
Take about 3 grammes, use rosolic acid or litmus as indicator, and apply 
the equation :— 
H,C,0,. 2H,0 + 2NH, . H,O = (NH,).C,0, + 4H,O 
caper geares agents lea int 


eo *)38 grms. NH, equivalent to 1000 c.c, oxalic acid solution. 
(2) Potassium hydrate or sodium hydrate or their solutions. 
Take about 1 gramme of solid, or about ro grammes of solution, use 
phenol-phthalein or litmus as indicator, and apply the equations :— 
H.C,O, ° 2H,O + 2NaHO = Na,C,O, +- 4H,O 
——_> 


8 
a — = grms. real NaHO, equivalent to 1000 c.c. acid. 
H.C,O, . 2H,O + 2KHO = K,C,0, + 4H,0 
ee 
2)126 2)i12 


7 56 =egrms. KHO, equivalent to 1000 c.c. acid. 


SLANDARD SOLUTION OF OXALIC ACID. 11 


(c) Metallic sodium (thrown on water and the resulting solution titrated). 
Take under °5 gramme, and use the equation :— 
H,C,O, . 2H,O + Na, = Na,C.O, + 2H,0 + H, 
ee 


—_ 
2)126 2)46 : 
es * grms. Nay, equivalent to 1000 c.c. acid. 


(@) Lime-water and lig. calcis sacch. 
Take about 25 grammes, use phenol-phthalein_or litmus, and apply the 
equation :— 
1.0.0, ° 2H,O a CaO + H,O a CaC,O0, + 4H,O 
— 


a 
2)126 2)56 
63 28 = grms. CaO, equivalent to 1000 c.c. acid. 
(e) Borax. 


Take between 2 and 3 grammes, use litmus as the indicator, and apply 
the equation :— 


ste enontee —————_ 
2)126 2)382 
63 191 = grms. borax, equivalent to 1000 c.c. acid. 


(/) Potassium permanganate. 
Take *5 to 1 gramme, dissolve in 50 c.c. of boiling water, acidulate with 
H,SO,, run in acid till decolorised, and apply the equation :— 
5(H,C,O, . 2H,O) + 4H,SO, + K,Mn,O, = 10CO, + 2MnSO, + 18H,O + 2KHSO, 
a See 


10)630 10)316 
63 31°6 grms. KMnO,, equivalent to 1000 c.c. acid. 


(C) Estimation of Alkaline Carbonates. 


By a similar process to (A), only conducted at a boiling temperature, so as 
to drive off all CO,, and the standard acid to be added until two minutes’ 
boiling fails to restore the color of the indicator. Another and better method 
is to use the volumetric sulphuric acid with methyl orange as the indicator, 
when the process can be conducted by simple cold titration, as the CO, does 
not affect this indicator. 


(a) Crystallised sodium carbonate. 
Take about 3 grammes, and use the equation :— 
H,C,0, . 2H,0 + Na,CO, . 10H,O0 = Na,C,0, + CO, + 13H,0 
Retin teammate? —— 
2)126 2)286 
63 143 =grms. Na,CO,10H,O, equivalent to 1000 c.c 
acid. 
(6) Dried sodium carbonate. 
Take about 1 gramme, and use the same equation less the 10H,O on 
each side :— | 


2)126 , 2)106 
63 53 — gims. Na,CO,, equivalent to 1000 c.c. acid. 


(c) Sodium bicarbonate. 
Take about 3 grammes, and use the equation :— 
H,C,0, . 2H,O + 2NaHCO, = Na,C,0, + 2CO, - 4H,O 
See eee” —_— 


2)126 2)168 
63 84 = grms, NaHCO, equivalent to 1000 c.c. acid. 


aA 


112 VOLUMETRIC QUANTITATIVE ANALYSIS. 


(2) Potassium carbonate (the B.P. requires 84 per cent. of the pure anhydrous 
salt (K,CO,) and the U.S.P. exacts 81 per cent.). 
Take about 2 grammes, and use the equation :— 
H,C,0O, ° 2H,O ae K,CO, a K,C.0, aa CoO, > 2H,O 
ee et eet 
2)126 2)138 
63 69 = grms. pure K,CO,, equivalent to 1000 c.c. acid. 
(ce) Potassium bicarbonate. 
Take about 2 grammes, and use the equation :— 
Hy; ° 2H,O aa 2KHCO, = K,C,0, + 2CO, + 4H,O 
~~ ——’” 
2)126 2)200 
63 100 = grms. KHCO,, equivalent to 10 oO c.c, acid. 
(f) Commercial “ carbonate of ammonia.” 
Take about 1 gramme, do not boil too violently, and use the equation :— 
3(H,C,O0, . 2H,O) + 2(N3HyC,05) = 3(NH,).C,0, + 4CO, + 8H,0 
—$ $$, ———” —__- 


6)378 6)314 
63 52°3 —grms., equivalent to 1000 c.c. acid. 


(D) Estimation of Lead. 


Weigh out the substance, dissolve it in plenty of water (the flask 3 full), 
with a drop or two of acetic acid to clarify it, and then carefully drop inithe 
standard acid till precipitation ceases. ‘Thus we operate upon :— 


(a) Plumbic acetate. 
Take 3 grammes, and use the following equation :— 
H,C,O,. 2H,O + Pb(C,H,0.), . 3H,0 = PbC,O, + 2HC,H;0, + 5H,0 
—_—_— ——$_ 


2)126 2)379 
63 189°5 = grms., equivalent to 1000 c.c. acid. 
(6) Liquor plumbi subacetatis. 
Take about 10 grammes, and use the equation :— 
2(H,C,O, . 2H,O) + Pb,O(C,H;0.)2. = 2PbC,O, + 2HC,H;O02 + 5H2O 
——_s ———_ $7 
4)252 4)548 


63 137 —grms., equivalent to 1000 c.c. acid. 


(Z) Estimation of Organic Salts of the Alkalies. 


Organic salts of potassium or sodium are examined by weighing out about 
2 grammes in a ¢aved platinum or porcelain crucible, and then heating to 
redness in contact with the air until all is perfectly charred. ‘The crucible 
is now cooled, and its contents dissolved in boiling water and filtered into 
a flask, and the filter washed with boiling water until the washings do not 
affect red litmus paper. The contents of the flask are then colored by the 
indicator and titrated with the standard acid, in the manner described above 
for alkaline carbonates. ‘The ignition causes the conversion of the organic 
salt into an alkaline carbonate. Thus we should operate upon :— 


(a) Cream of tartar. 
2KHC,H,0, + 50,—= K,CO,; + 7CO, + 5H,0 ; 
SS —— 








376 138 
then K,CO, + H.C,0, . 2H,O = K,C,O, + CO, + 3H,0; 
—_—o_— — 


138 126 
therefore H,C,O, . 2H,O = 2KHC,H,O, 
~~ — 


2)126 2)376 


63 = 188 = erms. of KHC,H,O,, equivalent to 1000 c.c. 
~ acid. 


STANDARD SOLUTION OF OXALIC ACID. 113 





(2) Neutral potassium tartrate. 
2(K,C,H,O,. H,O) + 50, = 2K,CO, + 6CO, + 6H,0; 
a 


=v ~~ 
488 276 
then 2H.C,0, . 2H,O + 2K,CO; = 2K,C,0, + 2CO, + 4H,O; 
on at ey — 


252 276 
therefore 2H,C,0, . 2H,O = 2K,C,H,O, . H,O 
a 


4)252 4)488 
‘lab ey = 122 = grms. of K,C,H,O,. HO, equivalent 
to 1000 c.c. acid. 
Note.—According to the U.S.P. the formula should be (K,C,H,O,),H,O, and therefore 
63 of acid (1000 c.c.) will equal 117°5 grammes. 


(c) Rochelle salt. 
2(KNaC,H,O,. 4H,O) + 50, = 2KNaCO, + 6CO, + 12H,0; 
SS >) —>—S—7Y” 


564 244 
then 2KNaCO, + 2(H,C,0,.. 2H,O) = 2KNaC,O, + 2CO, + 6H,O; 
econ eee etl eee ead 
244 252 
therefore 2(H,C,0, . 2H,O) = 2KNaC,H,O, 
Sa eee —_—_——_—_’ 
4)252 4)564 


63 = 141 = grms. of KNaC,H,O,. 4H,O, equivalent 
to 1000 c.c. acid. 








(2) Potassium citrate. 
2K,C,.H; O, Ue 90, — 3K,CO, = 9CO, ae 5H.O ; 
—_——_—" ia 


612 
ed —e 
414 378 
therefore 3(H,.C,0, ° 2H,O) — 2K,C,H,;O, 
SS eee” —_—_—_ 


6)378 6)612 
63 ~ 102 = grms. of K;C,H,O,, equivalent to 
1000 c.c. acid. 


Note—In the U.S.P. the formula is given as K,C;H;O, . H,O (= 648), and therefore 63 
of acid (1000 c.c.) will equal 108 grammes. 





(7) U.S.P. Standards of Strength by Oxalic Acid. 


C.c. re- 


Grms. taken. quired Per cent. of strength indicated. 
Ammonii Carbonas , . 2°616 : 50 100, of the salt. 
Aqua Ammoniz . a sO (ao C.c) ‘c.) , 50 10, of the dry gas. 
Aqua Ammonize F ortior Sea tel SO- 3.) 4 3 56 28, of the dry gas. 
Liquor Plumbi Subacetatis . 13°67 (11'2 ,,) . 25 25, of the basic salt. 
Liquor Potassze . : eer (2 97ees)e a 25 5, of the hydrate. 
Liquor Sodee ; ; . 20°00 (189 ,, ») : 25 5, of the hydrate. 
Potassa : : : her 2 OO as : 45 90, of the hydrate. 
Potassii Acetas. ; eco } : 49 98, of the salt. 
Potassii Bicarbonas . ets 00. « ; : 50 100, of the salt. 
Potassii Carbonas . : ae S'AS « : : 40°5 81, of anhydrous salt. 
Potassii Citras : S40. a Lae 50 100, of the crystallised salt. 
Potassii et Sodii Tartras a SS , : 25 100, of the salt. 
Potassii Permanganas . A een 785 . ; : 24°7 98°8, of the salt. 
Potassii Tartras . ; . 2°94 : , 25 100, of the crystallised salt. 
Soda . ‘ ; ; SueeIOO ics ; A 45 90, of the hydrate. 
Sodii Bicarbonas . RAO! ; ‘ 49°5 99, of the salt. 
Sodii Bicarbonas Venalis ca ZO ; 47°5 95, of the salt. 
Sodii Carbonas . a eh A ihe : : 49 98, of the crystallised salt. 
Sodii Carbonas Exsiccatus 2 OG: : : 36°3 72°6, of anhydrous salt. 
Spiritus Ammonize . aoc sOuee : ; 50 10, of the dry gas. 


8 


114 VOLUMETRIC QUANTITATIVE ANALYSIS. 


erg denser eer 


III. STANDARD SULPHURIC ACID. 
Equivalent N = 49 grams per litre. 
(A) Preparation. 

Measure out 28 c.c. of ordinary strong sulphuric acid, and dissolve it in a 
litre of water. When cool, place some of this rough acid in a burette, and 
check it against a solution of 2°62 grammes of pure sodium carbonate in water, 
using methyl-orange as the indicator. Note the number of c.c. of acid used, 
put 20 times this amount into the test mixer, and make up to 1 litre with water. 

Note.—Pure Na,CO, is best made by packing a percolator with good sodium bicarbonate and 
percolating with distilled water until the fluid, passing through, gives no reaction with AgNO, 
or BaCl, after acidulating with HNOs and HCI respectively. The contents of the percolator 
are then dried and heated to redness, and the residue saved as “ chemically pure Na,CO; for 
standardising acids.” 

(B) Uses. 


Can be used (with advantage) instead of standard oxalic acid for all pur- 
poses for which the latter has been above recommended, except the estimation 
of lead. Is specially useful for the estimation of alkaline carbonates when 
methyl-orange is used as indicator. Each c.c. of the acid contains ‘o49 grammes 
real acid, and exactly corresponds in strength to the standard oxalic acid 
already described. 


IV. STANDARD SOLUTION OF SODIUM HYDRATE. 


Strength :—Equivalent N = 40 grammes NaHO in 1000 6.6. 
(A) Preparation and Check. 


As commercial soda is not pure, this solution has to be made as follows :— 

Dissolve 45 grammes of ordinary caustic soda in 1 litre of distilled water, 
and let it cool to 15°5° C. (60° F.). Now place 20 c.c. of standard solution of 
oxalic acid in a flask, add phenol-phthalein or litmus, and run in some of this 
crude soda solution from a burette until neutrality is produced. Note the 
number of c.c. of soda used, put 50 times that volume of the crude solution 
into a test mixer, and make up to the rooo c.c. mark with distilled water. On 
again checking, 20 c.c. of the acid should take exactly 20 c.c. of the perfected 
soda for exact neutralisation. 

(B) Acidimetry. . 

Soda solution is used for taking the strength of acids by simply weighing 
out a quantity of the acid, and then running in the soda in presence of phenol- 
phthalein. We operate, as a rule, upon about r gramme of a strong or a solid 
acid, and from 5 to 10 grammes of a diluted acid. The following are some 
of the more important equations :— 

(2) NaHO + HCl = NaCl + H,O 
—— —— 
i849 36.5 grms. of HCl, equivalent to 1000 c.c. NaHO. 
(6) NaHO + HNO; = NaNO, + H,O 


—__—=-"2 Ss—_ ™ ~~” 





40 63 = grms. of HNO,, equivalent to 1000 ¢.c. NaHO. 
€c) NaHO ae HC,H,O, —_ NaC,H,0, + H,O 
——_— Vv 
40 60 = grms. of HC,H,0., equivalent to 1000 ¢.c. NaHO. 
(d) 2NaHO + H,SO, = Na,SO, + 2H,0 
—_—— =~” 
2)80 2)98 


4o = 49 = grms, of H,SO,, equivalent to 1000 ¢.c. NaHO. 
(ce) 2NaHO + H,C,H,Og = Na,C,H,O, + 2H20 
2)80 2)150 
40 75 = grms, of H,C,H,O,, equivalent to 1000 c.c. NaHO. 
(f) 3NaHO + H,C,H,O,. H,O = Na,C,H;O, + 4H,0 
—=\— ——— 
3)120 3)210 
40 70 = grms. of H,C,H;0,. H,0, equivalent to 1000 c.c.NaHO. 








STANDARD SOLUTION OF ARGENTIC NITRATE. 115 





(C) List of Strengths of the U.S.P. Acids, etc. taken by Soda. 


C.c. re- 


; d Grms. taken, quired. Percentage strength. 

Acidum Acetium ; : j Gos (57 cc.) 36 36, of absolute acid. 

is 4; (dilute). 2a ‘ 24. 6, i 

Poem ceetial) B80. 49°5 99, 9 

sa, Goltricum . 4 : : x5 ; 50°0 _—‘I00, °e 

», Hydrobromicum Dilutum 1616. ; 20 10, re 

», Hydrochloricum f 3°64. ; S15) ST:0, A 

+ - Dilutum 7326 Ge OFC.) mee TO; rT 

a Lacticoim : : ; 4°50. : 37'5 755 re 

», Nitricum , 3 : 215.4 ‘ 4270) 100°A, 5 

ce Ai Dilutum . LS OON TO or), ed 10, a 

», Sulphuricum . 3 ; Bus. : 48 96, - 

4 Ap Aromaticum 9°80 (10°3 c.c.) 36 18, of the total acids. 

* es Dilutum O80) (O'T1Gc.) — 20 10, of the absolute acid. 

ss .attaricum . , 4 chy S : 50 100, of the crystallised acid. 
Brandy , ‘ ; : : TOO CiC. 4s 3 fixed limit of acidity. 
Whiskey . i ; : 5 TOO Ses Bes 2 if 
Wine : ; ; ; . Z5GCor™ 5 15 to 26 i, 


(D) Checking the Strength of Chloral Hydrate 


This method is used in America, and is thus applied : 2 grammes of chloral 
hydrate are dissolved in 10 c.c. of water, this solution is tested for acidity by 
litmus paper, and if acid it is exactly neutralised by a few drops of very weak 
soda. 20 C.c. of volumetric soda are then added, and the whole is allowed 
to stand for half an hour to complete the decomposition into chloroform and 
sodium formate. Phenol-phthalein having been added, volumetric acid is run 
in from a burette till the color changes, and the number of c.c. of acid used 
having been deducted from 20, the difference gives the c.c.’s of soda used up 
by the chloral. Then on the equation 

2C,HCI,0.H,O + 2NaHO = 2CHCl, + 2NaCHO, + 2H,0 
each c.c. of soda so used represents ‘1655 grammes of chloral hydrate. 


V. STANDARD SOLUTION OF ARGENTIC NITRATE. 


ge = 17 grammes per 1000 6.6. 


(A) Preparation. 


Dissolve 17 grammes pure AgNQs in distilled water, and make up to 1 litre 
(1000 c.c.) 

Check.—As argentic nitrate is not always pure, the solution when thus 
made should be standardised by weighing out ‘1 (one decigramme) of pure 
powdered sodium chloride, dissolving it in water in a small beaker, adding 
sufficient solution of potassium chromate to color it yellow, and then running 
in the silver solution, with constant stirring, until the last drop just causes the 
color to change from yellow to pink. This should take 17°1 c.c. of silver 
solution if it be of correct strength, because :— 

AgNO, + NaCl = AgCl + NaNO, 


eye = 
10)170 10)58°5 N 
17 5°85 = grms. of NaCl, equivalent to 1000 c.c, To SNOs. 


(BL) Estimation of Soluble Haloid Salts. 


The silver solution is used for the estimation of haloid salts by weighing 
out any quantity ranging between ‘1 and ‘2 (one or two decigrammes), dis- 
solving, and titrating, K,CrO, being used as the indicator, exactly as above 
described. ‘Thus we should operate upon :— 


116 VOLUMETRIC QUANTITATIVE ANALYSIS. 
nnn eee aerne re 


(a) Potassium bromide. 
AgNO, + KBr = AgBr + KNO, 
— mee 


10)170 IO)119 N 
be 11-9 = grms. of KBr, equivalent to 1000 c.c. To ASNOs. 


(6) Ammonium bromide. 
AgNO, + NH,Br = AgBr + NH,NO, 


10)170 10)98 N 
17 9°8 = grms. of NH,Br, equivalent to 1000 ¢.c. 7 AgNO. 


wa(c) Sodium bromide, potassium todide, and sodium iodide, all by similar 


equations. 
NaBr + KI + Nal 
——’ . 


—— SS" 


10)103 10)166 I10)150 N 
10°3 16°6 15,0 all respectively = 1000 c.c, ToASN Os: 








Note.—Bromides, if adulterated with iodides, will take Jess silver than they ought, but, if 
the impurity be chloride, they will take more. Therefore they must neither take /ess nor 


more than the correct amount. 
(C) Estimation of Hydrocyanic Acid. 

Silver solution is also used for taking the strength of hydrocyanic acid. 
This is done by weighing out about 5 grammes, adding a drop of solution of 
litmus, and then a few drops of NaHO so as to cause strong alkalinity. Now 
carefully drop in the silver solution from the burette, with constant agitation, 
until a faint permanent cloud of AgCN is produced. If, during the operation, 
the litmus becomes red, more NaHO must be added to keep it blue; "At 
the moment that the permanent cloud appears the following reactions are 
complete :— 
2HCN + 2NaHO = 2NaCN +2H,0 


~~ —_—S—— 


54 98 
2NaCN + AgNO, = AgCN.NaCN + NaNO, 





98 170 
therefore— 2HCN = AgNO; 
Perea See —Vo 
10)54 10)170 
54 = 170 


N 
so that 1000 c.c. ToASNOs are equivalent to 5°4 grms. of HCN. 


On adding more silver AgCN would be precipitated thus :— 
NaCN. AgCN + AgNO, = 2AgCN + NaNO, ; 
and the first appearance of this precipitate therefore shows that the action to 
be calculated upon is complete. 
Potassium cyanide is done in the same way, using about ‘2 gramme, and 
AgNO; = 2KCN—~ze., 17 grammes (1000 ¢.c.) = 13°0 grammes KCN. 


(D) Application of Volhard’s Method to the Analysis of Chlorides. 

This process is, in certain cases, a much better method for the estimation of 
chlorides than the direct method with the chromate indicator, because it may 
be used in the presence of nitric acid, thus enabling a chloride to be estimated 
in presence of a phosphate or other acid which precipitates silver in a neutral 
solution. It depends upon entirely precipitating the chloride in the presence 
of nitric acid by a known volume of standard solution/of silver, and then esti- 
mating the excess of silver, left uncombined with the chloride, by standard 
solution of ammonium thiocyanate (sulphocyanate), using a drop of solution of 


STANDARD SOLUTION OF IODINE. 117 


ferric alum as an indicator. [The thiocyanate solution is made to contain=7°6 
grammes NH,CNS per litre, and is checked against the silver so as to correspond 
with it c.c. to c.c.] As soon as the thiocyanate has precipitated all the silver 
it will strike a blood-red with the ferric salt, due to the formation of ferric 
thiocyanate. ‘The difference between the volume of standard silver solution 


originally added and that of the thiocyanate used will give the c.c. of silver 
equivalent to the chloride present. 


(Z) Standards of U.S.P. Strength by Silver Solution. 
Grms, taken. C.c. used. Strength. 


Ammonium bromide . ; F "30 31°4 97% 
Hydrocyanic acid (diluted) . OFS 50° 2 oy real HCy. 
Potassium cyanide : - : 65 45'0 90%. 
i bromide ; ; , *30 257 O77. 

Sodium F F "30 29'8 97%. 
Syrup acid (hydriodic) . f ag 31:00 25°0 10of HI. 

», ferrous bromide . “ aed eh 50°0 10% FeBr,. 

sd »» . lodide i - Noell OY 6 50°0 10% Fel. 


VI. STANDARD SOLUTION OF IODINE. 


Tom 12°7 grammes per litre (1000 ¢.¢.) 


(A) Preparation. 


Weigh out 12°7 grammes of pure iodine, and place it in a litre flask with 
18 grammes of potassium iodide and about 200 c.c. of water, agitate till 
dissolved, and make up to one litre with water. 

Check.—To standardise the strength of the solution (if desired), test it 
against ‘2 gramme (2 decigrammes) of pure As,O3;, as hereafter described. 


(2) Estimation of Arsenious Acid. 

This solution is used :— 

For arsenious acid and the solutions thereof weigh out one to two deci- 
grammes of the As.O3, and dissolve it in boiling water by the aid of five 
times its weight of NaHCO3. Let it cool, add some mucilage of starch, and 
run in the iodine solution until a faint permanent blue color is obtained. 
Then apply the equation :— 

ay + as + 5H,O = 2H;AsO, + 4HI 


4)508 4198 
I0)127___10)49°5 N 
12°7 4°95 grms. of As,O,, equivalent to 1000 c.c. oe iodine. 








For Aguor acidi arsentost use 10 grammes and 2 grammes NaHCO. 
For “iguor potassit arsenitis use 10 grammes and 2 grammes NaHCOs. 


(C) Estimation of Sulphurous Acid. 


For sulphurous acid weigh out about one gramme from a stoppered bottle, 
and largely dilute it with water. Add starch mucilage, and run in the iodine 
solution until the faintest possible Zermanent blue appears. Then apply the 
equation :— 

I, + H,O + SO,.H,O = H,SO, + 2HI 
—— 


—~ 
10)127 10)32 


Me ola ‘ Doo 
12°7 3'2 grms. SO,, equivalent to 1000 c.c. om iodine. 


118 VOLUMETRIC QUANTITATIVE ANALYSIS. 





(D) Estimation of Thiosulphates (yfosulphites). 
For sodium thiosulphate (hyposulphite) use about *5 gramme, dissolve in 
water, add starch, and titrate as above. 
12°7/l==a4'Ss* hypo.” 


VII. STANDARD SOLUTION OF SODIUM THIOSULPHATE (“HYPO”). 
Strength :— ~ = 24'8 “hypo” (Wa,S,03 . 5H,O) per litre (1000 ¢.¢.) 


(A) Preparation and Check. 


Dissolve about 28 grammes of commercial “hypo” in a litre of distilled 
water. Now place 20 c.c. of standard solution of iodine slightly diluted with 
water in a beaker, and run in the rough “hypo” solution until the color 
changes to that of pale sherry. Then add mucilage of starch, and continue 
to run in the “hypo” till the last drop just discharges the blue color. Note the 
number of c.c. of “hypo” used, put 50 times that number into a test mixer, 
and make up with distilled water to 1000 c.c. 

This solution may be used for :— 


(2) Estimation of Free Iodine. 


By weighing out ‘2 gramme (2 decigrammes), dissolving in a little water 
by the aid of potassium iodide, and then running in ‘“‘hypo” till the color is 
reduced to that of a pale sherry; lastly, adding starch mucilage, and going 
on till the blue is just bleached. Then by the equation :— 

2(Na.S,03,5H,0) + I, = 2NalI + Na,S,O, + 10H,O 
ee A ed —— 





2)496 PAE 
10)248 10)127 ‘oN 
24°38 =  12°7 grms. I, equivalent to 1000 c.c. = ‘“hypo.” 


(C) Estimation of Free Chlorine or Bromine. 


For chlorine water or bromine water. 
Weigh about 10 grammes from a stoppered bottle, pouring it directly into 
a flask containing 2 grammes of potassium iodide dissolved in 50 c.c. of 
water, and then titrate with “hypo” as already described. 
The Cl first liberates an equivalent quantity of iodine from the KI, and 
the “hypo” then acts upon the I, so set free, thus :— 
Cl, -+ 2KI = 2KC1 +1, 
mops 


WH 
20)71 Z0j)254 ty 
3°55 12°7 
2Na,S,0,5H,O + I, = 2NaI + Na,S,0O, + 10H,O 
—— SS 


20)496_-20)254 





243 = 12°7, therefore 3°55 grms. Cl = 1000 c.c. = “hypo.” 
On the same principle, 
I, = Bry 
=< Sevres 
20)254 20) 160 N 
12°7 8:0, so that 8’o grms. Br is equivalent to 1000 c.c. 7 ““ hypo.” 


(D) Estimation of Available Chlorine. 


For chlorinated lime and its solution. 
Use ‘5 gramme of the solid or 5 grammes of the “guor. Put it into a 


STANDARD SOLUTION OF POTASSIUM BICHROMATE. 119 


A ———EE———————————————————————— Enea iininniia 


flask with 1°5 gramme of KI dissolved in 100 c.c. of water, and then drop 
in HCl in excess. Lastly, titrate with “hypo” as already described. Then 
by the equations :— 

(a) CaOCl, + 2HCl=CaCl, + H20 + Cle, 

Cl, + 2KI=2KCl + I,, 

c) 2(Na,S,O3 . 5H,O) + Ip=2Nal + Na,S,O, + 10H,O, 


we come to the result already shown for chlorine-water—namely, that 


2(Na.S,0, . 5H,.0) = I, = Cl, 
So a. hee 
20)496 20)254 20)71 
ce Ns dG Fa EET 


N :, 
therefore, 1000 C.c. — hypo” represent 3°55 grammes “ avat/able chlorine” in 
all chlorinated compounds. 


Liquor sode chlorinate. 


Use about 5 grammes, and proceed as for chlorinated lime. The action 
and calculations are the same, only differing in the first equation, which is 


Na,OCl, + 2HCl=2NaCl + H,O + Cy. 
(Z) List of U.S.P. Standards by Iodine and “Hypo.” 


IODINE SOL. 

Grms. taken. C.c. required. Per cent. of strength indicated. 
Acidum arseniosum . é .  0°247 48°5 97, of the anhydride. 
Acidum sulphurosum_ . : F238 I4 3°5, of the dry gas. 
Liquor acidi arseniosi . . + 24°70 48°5 .0°97, of the anhydride. 
Liquor potassii arsenitis . . 24°70 48°5 0'97, of the anhydride. 
Potassii sulphis  . ; ~ 0485 45 go, of the crystallised salt. 
Sodii bisulphis. . : - 0°26 45 go, of the salt. 
Sodii sulphis . ; : = < Ots 45 go, of the crystallised salt. 

‘* Hypo” SOL. 

Grms. taken, C.c. required. Per cent. of strength indicated. 
Aquachlori . é e354: 40 o°4, of chlorine. 
Calx chlorata . r 4 5 er OLzE 50 25, of chlorine. 
Iodum_. : ‘ ; 0°633 BO roo, of iodine, 
Liquor iodi compositus . 12°66 50 5, of iodine. 
Liquor sodz chlorate . A . 8°88 (8°5c.c.) 50 2, of chlorine, 
Tinctura iodi . Ss ats oo 6°33 40 8, of iodine. 


VIII. STANDARD SOLUTION OF POTASSIUM BICHROMATE. 


IN é 
Strength Fo 14°75 Svammes K,Cr,O07 im 1000 66. 


(A) Preparation. 


Dissolve 14°75 grammes pure K,Cr,O, in one litre of water. 

Check.—If desired to standardise, we do so by performing an estimation 
upon ‘5 gramme (5 decigrammes) of pure iron (pianoforte) wire, dissolved in 
dilute H,SO, as described below. 

Principle of the Process.—K,Cr,O,, when heated with an acid (say H,SO,), 
gives 

K,Cr,0, + 4HSO, = K,SO, + Cr.(SO,)3 + 4H,O + Og; 
therefore, each molecule of bichromate gives three atoms of nascent oxygen, 
which possesses the power of raising six atoms of iron from the Jerrous to the 
ferric state, because 

6FeO + O; = 3Fe,03. 


120 VOLUMETRIC QUANTITATIVE ANALYSIS. 











(B) Estimation of Ferrous Salts. 


Bichromate solution is to be used for the following estimations :— 
(a) Metallic tron. 


‘5 gramme of the metallic wire or filings is dissolved by the aid of heat 
in dilute sulphuric acid, using a flask fitted with a cork through which passes 
a small tube to allow the exit of steam and hydrogen, but to prevent as far as 
possible ingress of air. While the iron is dissolving, 2 ounces of water are 
placed in a basin over the gas, and a burette charged with bichromate solution 
is arranged over it. A porcelain slab is also got ready at the right-hand side 
of the basin, and is covered over with spots, from a glass rod, of freshly made 
solution of potassium ferricyanide. When dissolved, the iron solution is rinsed 
from the flask into the basin, and immediately titrated with the bichromate, 
until a drop taken from the basin on the stirring rod just ceases to give a blue 
color when brought into contact with one of the spots of potassium ferricyanide 
on the slab. The number of c.c. of bichromate solution used is read off, and 
the following equations applied :— 

6Fe + 6H,SO, = 6FeSo, + 3H, 
S—_ —~_ 


20)336 20)912 





16°38 45'6 
6FeSO, + K,Cr,0, + 7H,SO, = 3Fe.(SO,)3 + K,SO, + Cr(SO,)3 + 7H,0 ; 
—,—"’ SS _—_" 
20)912 20)205 
45°6 14°75 . 
therefore 14°75 K,Cr,.O, = 16°8 Fe grammes, equivalent to 1000 cc. er 
bichromate. 


(2) For ferrous sulphate, ferrous phosphate, ferrous arseniate, and /ferrz 
carbonas saccharata, 


Use about 1 gramme in each case, dissolve in water by the aid of sulphuric 
or hydrochloric acid, then add a good excess of dilute H,SO, or HCl, 
and titrate with bichromate solution as already described. Apply the 
equations as under :— 


(1) Crystallised ferrous sulphate. 
K,Cr,0, + 6FeSO, . 7H,O + 7H.SO, = 3Fe.(SO,); + KSO, + Crs(SO,)3-+ 14H,O 
—— —$—_—_, ' - 


20)295 20)1668 
eens : Ne 
14°75 83'4 = grms., equivalent to 1000 c.c. om bichromate. 





Note.—If 4°167 grammes be weighed of this substance and titrated, then the number 
of c.c. of bichromate used multiplied by two equals the percentage of un- 
oxidised ferrous sulphate present. 


(2) Real ferrous sulphate. 
K,Cr,0, + 6FeSO, + 7H,SO, = 3Fe(SO,)3 + K,SO, + Cr(SO,)3 + 7H30 
——— —>—" 
20)295 20/912 N 
14°75 45°6 = grms., equivalent to 1000 c.c. an bichromate. 
(3) Ferrous phosphate. 
K,Cr,O, + 2Fe,(PO,), . 8H,O + 7H,SO, = Fe,(SO,)3 + 2Fex(PO,)2 + K,SO, + 
gCr,0, + 3(PO,)> 20 + 7H,SO, (SO4)3 PCr(80,), 4 1sH,0 
20)295 20) 1004 N 
14°75 50°2 = grms., equivalent to 1000 c.c. 55 bichromate. 


_— 


STANDARD SOLUTION OF POTASSIUM BICHROMATE. 121 


(4) Ferrous arseniate. 
K,Cr,O, + 2Fe,(AsO,)y + 7H,O + 7H,SO,= Fe,(SO,); + 2Fe,(AsO,)) + K,SO,+ 
—_—_—— 


———’ 
20)295 20)892 eee [Cr(SO,)3 + 14,0 
1475 44°6 = grms., equivalent to 1000 c.c. =~ bichromate. 


(5) itd carb. sacch. (dissolve in HCl, because H,SO, would char the 
sugar) :— 


K,Cr,0, + 6FeCO, + 26HCI = 3Fe,Cl, + 2KCl + CrCl, + 6CO, + 13H,O 
—— ——J/’” 
20)295 20)696 


——— : ieee 
14°75 34'8 = grms., equivalent to 1000 c.c. cn bichromate. 


(C) Estimation of Ferric Salts. 


The process may be applied to ematite or any form of ferric iron by 
dissolving in excess of hydrochloric acid, and then dropping in zinc so as 
to evolve H, and reduce the iron to the ferrous state. When all Zn has 
dissolved, and the solution has ceased to give a red with KCNS, it is titrated 
with bichromate in the usual way. The reduction of the iron may be also 
readily, and in some cases preferably done, by the use of sodium sulphite 
instead of zinc, and then boiling off the excess of SQg. 


(D) US.P. Standards by Bichromate Solution. 


Grms. taken. C.c. used. Percentage strength. 
Reduced iron . ‘ : : -— — 80 
Crystallised ferrous sulphate . 4°167 a 
Precipitated) " A‘I at each c.c. used = 2 per cent. 
Dried Pe = . — an oe 
Saccharated ferrous carbonate . 8°00 33 15 per cent. 


Instead of bichromate we may use a standard solution of potassium 
permanganate to estimate iron, simply running it in (in presence of excess of 
H,SO,) until a permanent pink color remains. Each molecule of K,Mn,O, 
gives O;, and therefore equals ten atoms of Fe in oxidation. The solution 
is made by dissolving 3:16 grammes of permanganate in a litre of water. 
Taking such a solution each c.c. will equal z5455 of the molecular weight of 


IX. FEHLING’S STANDARD SOLUTION OF COPPER. 
(A) Manufacture and Check by the Ordinary Method. 


This solution is used for the estimation of sugars, and is made in two parts 
as follows :— 
No. I. 
Take of 
Sulphate of copper (pure crystals) . : . + 34639 grammes. 
Distilled water ; , ; : : erred se ge 
Dissolve the sulphate of copper in a sufficient quantity of distilled water to 
produce the volume required by the corresponding formula above given. 


Nomz: 
Tartrate of potassium and sodium : , ; . 173 grammes. 
Soda (U.S.P. 1880) . ; ; : eas » 60 F 
Distilled Water ; . . enough to make 500 c.c. 


Dissolve the tartrate of potassium and sodium and the soda in a sufficient 
quantity of distilled water to produce the volume required by the correspond- 


122 VOLUMETRIC QUANTITATIVE ANALYSIS. 


rE 


ing formula above given. Set the mixture aside until the suspended impurities 
have been deposited ; then remove the clear solution with a siphon. Keep 
both solutions separately. For use, mix equal volumes of both solutions, 
by pouring the copper solution into the alkaline solution. On heating the 
liquid in a test-tube to boiling, it should remain perfectly clear. Each 10 c.c. 
of this liquid will represent— 


Glucose . : : ; : : ; : : . ‘05 gramme. 
Maltose . ; : ; r ; ; : : - "082 as 
Inverted cane sugar . 7 : : : ; ; . "ogre tars 
Inverted starch : : ; : : : : - 045 s 


To check Fehling’s solution, weigh out ‘475 gramme of pure sugar candy 
and dissolve it in 100 c.c. of water in a small flask ; add 3 drops of strong 
HCl, and boil briskly for ten minutes to invert the cane sugar into glucose. 
Let it cool, neutralise with KHO, and then make up exactly to 100 c.c. with 
distilled water. Place this liquid in a burette arranged over a basin placed 
over the gas, and containing 10 cc. of Fehling’s solution and 50 c.c. of 
water. When the contents of the basin are boiling, run in the sugar solution 
until all blue color is destroyed. Then note the number of c.c. of sugar 
solution used, and whatever that number may be, it will contain the equiva- 
lent in sugar of 10 c.c. of “Fehling.” If the “ Fehling” be correct, 10 c.c. 
of the standard sugar will be used to entirely precipitate it. 

It is usually necessary to do the estimation twice, first roughly and 
then accurately, using the second time drops of K,FeCy, acidulated with 
acetic acid, on a slab, as an indicator for the disappearance of the last trace . 
of Cu from solution. 


(B) Manufacture and Check by Pavy’s Method. 


Cuprous oxide dissolves in ammonia, forming a colorless liquid. Taking 
advantage of this point, Pavy treats an ammoniacal cupric solution at a 
boiling temperature with sufficient saccharine solution to exactly discharge 
the blue color. The advantage of this method over that above described 
lies simply in the fact that there is no bulky red precipitate to interfere with 
the ready observation of the end reaction. To prepare the test solution, 
dissolve 20°4 grms. of Rochelle salt and the same weight of caustic potash 
in distilled water; dissolve separately 4°158 grms. of pure cupric sulphate in 
more water with heat; add the copper solution to that first prepared, and 
when cold, add 300 c.c. of strong ammonia, and distilled water to 1 litre. 
The process is conducted as follows: 10 c.c. of the ammoniated cupric solution 
(=o0'005 grm. of glucose) are diluted with 20 c.c. of distilled water, and 
placed in a small flask. This is attached by means of a cork to the nozzle of 
a burette, fitted with a glass stopcock, and previously filled with the saccharine 
solution previously diluted to a fixed bulk. The cork of the flask should be 
traversed by a small bent tube, to permit steam to escape. Now heat the 
flask until the blue liquid boils. Turn the stopcock in order to allow the 
saccharine solution to flow into the hot solution—which should be kept at the 
boiling point—at the rate of about 100 drops per minute (not more nor much 
less), until the azure tint is exactly discharged. ‘Then stop the flow, and note 
the number of cubic centimetres used. ‘That amount of saccharine solution 
will contain 5 milligrammes of glucose. To render the determination as 
accurate as possible, the solution for analysis should be diluted to such an 
extent that not less than 4 nor more than 7 c.c. are required to decolorise the 
solution. 

To find the percentage of sugar, multiply o*oo5 by the original total 
bulk (in c.c.) of the solution started with, and divide the product by the 


ESTIMATION OF PHOSPHORIC ACID. 123 


number of cubic centimetres of solution used from the burette. To observe 
easily the exact end reaction, a piece of paper or other white body should be 
placed behind the flask. Mr. Stokes uses the half of an ordinary opal gas 
globe fixed in the proper position. If the operator objects to the escape of 
the waste ammoniacal fumes, they may be conducted by a suitable arrange- 
ment into water or dilute acid. For a special apparatus for this purpose 
see the Analyst, vol. xil. 


(C) Estimation of Sugar. 


The sugar weighed must not exceed ‘5 gramme, and must be dissolved 
in 100 c.c. of water. If the sugar be either glucose or maltose or lactose it 
is titrated directly ; but if cane sugar, it is first inverted as above described. 
By always placing ro cc. of “Fehling” in the basin, then whatever 
number of c.c. of sugar solution we use, that number will contain the 
equivalent of 10 c.c., and we have only to calculate :— 


As No. of c.c. used : Total volume of sugar solution : : Equivalent of 10 c.c. ‘‘ Fehling ” of 
the sugar in question: Real sugar present in the quantity weighed out for analysis. 


(D) Estimation of Starch. 


Starch is weighed and boiled in a flask with water containing dilute hydro- 
chloric acid, under an upright condenser, for some hours. It is then cooled, 
neutralised with potassium hydrate, diluted to a fixed volume (not stronger 
than 1 in 200), and then the solution so made is titrated into Io c.c, of 
“ Fehling.” A much improved process will be found in Chapter x 


X. ESTIMATION OF PHOSPHORIC ACID 


is performed by means of a standard solution of uranic nitrate in the presence 
of sodium acetate. The necessary solutions are,— 

rt. Standard solution of uranic nitrate, made by dissolving 70 grammes in 
goo c.c. of water, and then, after ascertaining its strength by performing an 
analysis of 50 c.c. of the standard phosphate solution, diluting with water so 
that so c.c. will correspond exactly to 50 c.c. of that solution. If absolutely 
pure uranic nitrate were obtainable, theory requires the solution of 71 grammes 
in one litre of water to yield a solution which will balance the standard phos- 
phate (each 1 c.c. = ‘or gramme of P,O;). 

2. Standard phosphate solution, made by dissolving 50°42 grammes of 
perfectly pure disodium hydrogen phosphate in one litre of water, when each 
t c.c. will equal ‘or gramme of P,O;,. 

3. A solution of roo grammes of sodium acetate and 100 grammes of acetic 
acid in water, and the whole diluted to one litre. 

4. Finely powdered potassium ferrocyanide. 

To perform the process, the solution of the phosphate in about 50 c.c. of 
water is placed in a basin on the water bath, mixed with 5 c.c. of solution 
No. 3 (sodic acetate), and No. 1 (uranic nitrate), is run in from a burette, 
until a drop taken from the basin on to a white plate just gives a brown color, 
when a little powdered ferrocyanide is cautiously dropped into its centre. The 
number of c.c. of uranic solution used having been noted, the usual calcula- 
tions are to be applied. 

After repeated trials upon 50 c.c. of the standard phosphate solution, so 
as to thoroughly adjust the strength of the uranic solution, and at the same 
time accustom the eye to observe the exact moment of the appearance of the 
brown coloration, the process may be practically applied to Maunures. 


124 VOLUMETRIC QUANTITATIVE ANALYSIS. 


The best method of preparing the solution of the manure is to heat 1o 
grammes to dull redness for 15 minutes, and when cold to reduce it to a fine 
powder in a mortar, and add gradually 10 grammes of sulphuric acid diluted 
to 200 c.c. with water. Rinse the whole into a stoppered bottle, and make 
up with water to one litre. Shake up occasionally for an hour, and having 
then let all settle for three hours, draw off 100 c.c. (= 1 gramme manure) for 
analysis. ‘To thisadd a little citric acid (10 drops of a cold saturated solution), 
and slightly supersaturate with ammonium hydrate. Again acidify with acetic 
acid, add 10 c.c. sodium acetate solution, and then use the uranic solution as 
usual. If all these quantities be rigorously adhered to, each c.c. of uranic 
solution used can, without further calculation, be taken as indicating 1 
per cent. of tricalcium phosphate in the manure. 

This process is highly recommended by Mr. Sutton of Norwich, and elabo- 
rate details will be found in his work on Volumetric Analysis. 


XI. STANDARD SOLUTION OF BARIUM CHLORIDE. 
Semi-normial = 104 grammes per 1000 «6. of BaC?,. 


This is used for taking the amount of a soluble sulphate, by adding it toa 
known weight of the sulphate ; dissolve in water acidulated with hydrochloric 
acid, until precipitation ceases. ‘The process, however, is tedious, and the 
end of the reaction is not sharp, and it is therefore rarely employed. ‘The 
following is a specimen of the reaction, using magnesitim sulphate :— 


MgSO,.7H2O + BaCl, = BaSO, + MgCl, + 7H.O. 


Each c.c. of the standard solution equals o4 SO; or ‘048 SO,. 
The solution is made by dissolving 104 grammes of pure barium chloride 
dried at 220° F. in 1 litre of water. 


XII. STANDARD MAYER’S SOLUTION. 


Made by dissolving 13°546 grammes of pure mercuric chloride and 49°8 
grammes of potassium iodide in water, and then making up to 1000 c.c. 

This solution is used for the estimation of alkaloids, which should be free 
from any mucilaginous matter and preferably dissolved in a little dilute 
sulphuric acid. The reagent is added till precipitation ceases, and the exact 
equivalent for each alkaloid should be practically checked by operating on 
a known weight of the pure alkaloid, and then always using the solution 
under exactly the same conditions in future analysis. In the author’s hands. 
the process has not worked very well, except for the amount of emetine in 
tpecacuanha, which may be rapidly ascertained as follows :— 

I5 grammes of ipecacuanha are treated with 1°5 c.c. of dilute sglpbitite 
acid, and sufficient alcohol of 80 per cent. added to make the whole bulk up 
to 150 grammes. ‘The whole is allowed to stand for 24 hours, and 100 c.c. are 
decanted off for analysis. The liquid is evaporated until all the alcohol is 
driven off, and then brought under the burette containing the test solution, 
which is run in until it ceases to give a precipitate. The final point of the 
reaction is ascertained by filtering off a drop or two in a watch-glass placed 
on black paper, and adding a drop of the reagent, when, if no cloudiness 
appear, the precipitation of the alkaloid is complete. The number of c.c. of 
the test used multiplied by ‘o18g gives the amount of alkaloid in 10 grammes 
of the sample, which again multiplied by 10 gives percentage. 


ANALYSIS BY THE NITROMETER. 125 





XIII. ANALYSIS BY THE NITROMETER. 
(A) General Remarks. 


This useful instrument is illustrated in fig. 29. It consists of a measuring 
tube (a) graduated in cubic centimetres, having a funnel-shaped cup (c) 
connected to it by means of the stopcock (p). This cock is a “ three-way” 
one, and according to the direction in which it is turned, it can make 
connection and discharge the contents of the cup either into the tube a 
or out in the waste opening at E; or it can make, or quite shut off, all 
connection between a and the outer air through £. Connected to a by a 
piece of flexible indiarubber tube is the ungraduated control tube B. The 
object of the apparatus is the rapid and accurate measurement, at definite 
temperature and pressure, of gases evolved during any reaction; and it takes 
its name from the fact that it was first used to measure the nitric oxide given 
off by the decomposition of nitric acid. Suppose that we 
fill the instrument with a fluid (say mercury) right up to 
the top: having closed the tap p, we lower the tube B 
and then admit a little carbonic anhydride through E; by 
opening and again closing the top, we have a volume of gas 
in the measuring tube which we desire to measure under 
definite condition. If (1) we allow the instrument to stand 
until its contents must have assumed the temperature of 
the room, then a centigrade thermometer suspended to the 
same stand will give the temperature of the gas; (2) If we 
now raise or lower the control tube so that the level of the 
liquid both in it and in the measuring tube is the same, 
it is evident that the pressure inside A is the same as in 
the room,: and reference to a barometer standing near 
will give that pressure. It now only remains to read off 
the volume of the gas in the measuring tube, and having Fig. 29. 
corrected it to normal temperature and pressure by Charles’s and Boyle’s 
laws respectively, to calculate it from its volume in c.c, to its weight in 
grammes by multiplying the number of c.c. of volume at N.T.P. by the 
weight of 1 c.c. of the gas in grammes. This latter is easily obtained by 
multiplying the crith (0896 gramme, weight of 1 litre of H) by the atomic 
weight of an elementary, or half the molecular weight of a compound, gas, and 
then dividing by rooo. Suppose, for example, that in the analysis of a 
nitrate or nitrite we have obtained 20 c.c. of nitric oxide at 15° C. and 750 
m.m. barometer, and we require to know the weight of NO so got, that we 
may afterwards calculate therefrom the weight of the nitrate present, we 
should say :— 

(2) (273 + 0) X 750 X 20 
ae 15) X 760 
70896 X 15 __, ; 

(d) OS aha aeallars 001344 grm., weight of 1 c.c. NO. 

(c) 18°788 X ‘001344 = ‘0253 grm., weight of NO found. 

The various possible applications of this instrument are so numerous that an 
exhaustive detail would be impossible in the present work ; but the following 
should be practised as typical instances of its use :— 



































= 18°788 c.c., corrected volume at N.T.P. 


(B) Estimation of the Strength of Spirit of Nitrous Ether. 


The active principle of this drug is ethyl nitrite. Nitrites when mixed 
with excess of potassium iodide and acidulated with sulphuric acid cause 


126 VOLUMETRIC QUANTITATIVE ANALYSTS. 


a liberation of iodine, and evolve all their nitrogen in the form of nitric oxide, 
thus :— 
C,H; . NO, + KI + HosOrs C,H, . HO + KHS0,; a I a NO. 


The process (originally due to Mr. Allen) has been recognised officially for 
the assay of the spirit, and is thus conducted. The nitrometer is filled 
with saturated solution of sodium chloride, with which, owing to its density, 
a strong spirit will not readily mix, and so we save the expense of mercury ; 
5 c.c. of the sample to be tested is placed in the cup of the nitrometer, 
and the control tube having been lowered, the spirit is allowed to enter 
through the tap, taking care that no air gets in at the same time. 5 C.C. 
of a strong solution of potassium iodide is next allowed to enter, and this 
is in turn followed by 5 c.c. of dilute sulphuric acid. Effervescence imme- 
diately occurs, and if the tube be vigorously agitated at intervals, the reaction 
completes itself in to minutes. The level of the liquid in the control tube 
of the instrument is adjusted to equal that in the measuring tube, and the 
volume of nitric oxide is read off and calculated. For official purposes it is, 
however, sufficient to see that the resulting gas is seven times (or at all 
events not less than five times) the volume of the spirit started with.* The 
least trace of air allowed to enter with the liquids vitiates the results of the 
process, because the nitric oxide would be thereby converted into a higher 
oxide of nitrogen, and so become soluble in the fluid with which the instrument 
is charged. ‘The gas produced should be tested for purity by seeing that it 
js entirely absorbed by ferrous sulphate solution. 


(C) Estimation of the Strength of Sodium Nitrite. 


Weigh out ‘1 gramme of the salt, and dissolve it in the smallest possible 
quantity of water. Rinse this into the nitrometer cup, and proceed as in 
(4). A proper sample should yield 32°5 c.c. of gas, which should be entirely 
absorbed when a strong solution of ferrous sulphate is introduced. 


(D) Estimation of Nitric Acid in Nitrates. 


This depends on the fact that when a nitrate is shaken up with excess of 

sulphuric acid and mercury the following reaction takes place :— 
2KNO;3 + 4H,SO, + 3Hg = 3HgSO,+ K,SO + 2NO + 4H,O,— 
thus showing that each molecule of the nitrate radical NOs3 gives off a 
molecule of NO. If any chlorides or other haloid salts be present they are 
first removed by adding a slight excess of argentic sulphate to the solution 
and filtering. No quantity of a nitrate exceeding 2 decigrammes should be 
used, otherwise more gas may be evolved than the instrument will con- 
veniently hold. The nitrometer is charged with mercury, and the nitrate 
solution, which should not exceed 5 c.c., is put into the cup and passed 
therefrom into the measuring tube, followed by excess of strong sulphuric 
acid. ‘The instrument is well agitated for some time, and when action has 
ceased and the contents have cooled down to the temperature of the room, 
the level is adjusted and the volume of NO read off and calculated. All 
the precautions already mentioned must be observed. [If any nitrites be 
present, they affect the accuracy of the estimation, being also decomposed 
to nitric oxide. 
(Z) Estimation of a Soluble Carbonate. 


This has been proposed for use in taking the strength of the medicinal 
solution of ammonium carbonate in the spirit known as spzrifus ammonie 
aromaticus. A given volume of the spirit is placed in the cup and introduced 
into the nitrometer charged with mercury. ‘This is followed by an excess of 


* The U.S.P. requires 5 per cent. of ethyl nitrite. 


ANALYSIS BY THE NITROMETER. 127 





dilute hydrochloric acid, and the carbon dioxide evolved by the action of the 
acid upon the carbonate is measured. From this the percentage of ammonium 
carbonate may be calculated, or an empirical comparison of volume on the 
principle of that already described for spirit of nitrous ether may be applied. 
According to Mr. Gravill, the originator of the test, good aromatic spirit of 
ammonia should give off seven times its volume of carbon dioxide after allowing 
a correction for the slight solubility of the gas in the liquid with which it is 
inclosed. The U.S.P. requires 4 per cent. of ammonium carbonate. 


(7) Estimation of the Strength of Solutions of Hydrogen Peroxide. 


This depends upon the fact that, when hydrogen peroxide acts upon 
potassium permanganate, acidulated with sulphuric acid, oxygen is evolved. 
One half of this oxygen is due to the peroxide and the other to the perman- 
ganate. The nitrometer should be charged with concentrated solution of 
sodium sulphate (which in this case is better than brine), and one cubic 
centimetre of the solution is introduced from the cup, followed by excess 
of a strong solution of potassium permanganate acidulated with sulphuric 
acid. The contents of the measuring tube, after the reaction is complete, 
must remain colored violet, thus showing that sufficient permanganate has been 
employed. A solution commercially described as of ro per cent. strength by 
volume should when thus treated give off twenty times its volume of oxygen. 


(G) Estimation of Urea in Urine. 


This process depends on the fact that when urea is decomposed by an 
alkaline hypobromite or hypochlorite, it gives off its nitrogen in the free 
state, the following reaction taking place :— 

N,H,CO + 3NaBrO = 3NaBr + N, + CO, + 2H,0. 

A small flask is fitted with a tight cork, through which passes a funnel 
tube closed by a clamp and reaching to the bottom of the flask, and also 
a bent delivery tube just passing through the cork. 5 cc. of the urine is 
placed in this flask, and the nitrometer having been filled with water the flask 
is attached to the tap of the nitrometer at the end E (see fig. 29, page 125). 
20 c.c. of a solution of bromine in sodium hydrate solution is then placed 
in the funnel and allowed to run into the urine, and the clamp immediately 
closed. At the same moment the tap of the nitrometer is so placed as 
to establish connection between E and the measuring tube. A little warm 
water in a basin is applied to the flask to hasten the reaction, and when no 
more gas is evolved, the tap is closed, the temperature and pressure adjusted, 
and the volume read off as usual. Each c.c. of gas at N.T.P. represents 
‘oo29 gramme of urea present in the 5 c.c. of urine acted upon. 

Fig. 29a represents a very simple apparatus that can be improvised in a 
shop or dispensary. 5 c.c. of urine are placed in the test tube (A), and 20 C.c. 
of hypobromite solution (or strong “guor 
sode chlorinate will do as well) into the 
bottle 8. The bottle c is filled with 
water, and its delivery tube is suspended 
in a graduated c.c. measure. When all § 
is tight the urine is caused to mix with |} 
the reagent by tipping up B, and the gas _ 
produced passing into c displaces water, 
which latter runs intothe measure. The 
number of c.c. of water thus collected in 
the measure multiplied by ‘058 gives the percentage of urea in the urine. It 
is manifest that 1 fluid dram may be taken, and the measure used may be an 
ordinary 2 oz. dispensing one (where only English weights and measures are 
handy), when each fluid dram of water in the measure at the finish will equal 
‘29 per cent. of urea. 





128 VOLUMETRIC QUANTITATIVE ANALYSIS. 


XIV. COLORIMETRIC ANALYSIS. 
General Remarks. 


This is a variety of volumetric analysis in which the amount of a substance 
present in solution is found by adding, to a given volume, a fixed quantity of 
a reagent and observing the color produced. This color is then matched 
by adding, to an equal volume of distilled water, the same mixed quantity of 
reagent, and running in a volumetric solution of the pure substance until the 
same tint is produced. Evidently when this point is reached the amount of 
substance present in the solution under analysis equals that in the volumetric 
solution used for the comparative experiment. The applications commonly 
occurring of this method are :— 


(A) Estimation of Ammonia by “ Nesslerising.” 
Forithis process the following solutions and apparatus are required :— 


(a) Nessler’s solution. Dissolve 35 parts of potassium iodide in 100 
parts of water. Dissolve 17 parts of mercuric chloride in 300 
parts of water. The liquids may be heated to aid solution, but 
if so must be cooled. Add the latter solution to the former 
until a permanent precipitate is produced. Then dilute with a 
20 per cent. solution of sodium hydrate to 1000 parts; add 
mercuric chloride solution until a permanent precipitate again 
forms; allow to stand till settled, and decant off the clear 
solution. ‘The bulk should be kept in an accurately stoppered 
bottle, and a quantity transferred from time to time toa small 
bottle for use. The solution improves by keeping. 


(6) Standard ammonia solution. Dissolve 3°15 grammes pure ammo- 
nium chloride in 1000 c.c. of distilled water free from ammonia. ~ 
For use, dilute 10 c.c. of this solution to 1000 c.c. with ammonia- 
free distilled water. Each c.c. of the diluted solution will then 
contain ‘ot milligramme of NH, (z.e. ‘oooor gramme). 


(c) Zwo narrow cylinders of colorless glass, of perfectly equal height . 
and diameter, holding about 70 c.c., and graduated at 50 c.c. 
These should either have a milk glass foot or should stand 
upon a perfectly white paper. 


(d) A pipette to deliver 2 c.c. 


(e) A quantity of ammoniafSree distilled water. This is obtained by 
placing a litre of ordinary distilled water in a retort, attaching 
a condenser (see Chap. I., page 4), and distilling until what 
passes over ceases to give any color with ‘“ Nessler’s solution.” 
The remaining water in the retort is then cooled and bottled 
for use. 


The liquid in which ammonia is to be estimated (usually a distillate ob- 
tained in water analysis) is first made up to a fixed bulk, and the bulk noted. 
It must be so diluted that it only gives a color and not a precipitate with 
“Nessler.” 50 c.c. of this solution are placed in a cylinder, and 2 c.c. 
of “ Nessler” having been added by the pipette, and the whole stirred with 
a perfectly clean rod, the color produced is observed. A little experience 
soon teaches the operator to judge the probable amount of ammonia solution 
required to produce a similar tint. Let us suppose, for example, that the 
color is judged to be equal to 2 c.c. of ammonia, then we proceed to confirm 


COLORIMETRIC ANALYSIS. 129 


our idea: 2 c.c. of the standard ammonia solution are run from a burette 
into the other cylinder, ammonia-free water is added to 50 c.c., then the 
2 c.c. of “ Nessler,” and the whole stirred with the clean rod. If now, after 
a few minutes, the colors match, we are correct; but if not, then we must try 
again and again with more or less standard ammonia until we get an exact 
match between the colors in the two cylinders. ‘This having been attained, 
the calculation is very simple, and will be best explained by an example. 
Suppose that we start with a distillate containing ammonia and made up 
to 200 c.c., and that we employ 5 c.c. of standard ammonia solution in the 
comparison experiment, to match the color produced by ‘‘ Nessler” in 50 c.c. 
Omeucn cistillate. Then 5 c.c.x ‘or = °o5, and ‘05 x4 = ‘2; ‘therefore the 
whole 200 c.c. of distillate contained ‘2 milligramme of NH;. Beginners 
should train their eyes by observing the colors produced by adding various 
quantities of standard ammonia to 50 c.c. of ammonia-free water, and then 
introducing the ‘‘ Nessler.” 4, of ac.c. of standard ammonia will produce 
a very faint yellow, while larger amounts will increase the color to orange, 
and finally to deep orange-red. We should always wait 3 minutes before 
observing, as the full color does not appear under that time. 


(B) Estimation of Nitrites in Water. 
See Water Analysis, Chapter X. 


(C) Estimation of Minute Quantities of Copper or Iron. 


This has often to be done in articles of food, such as preserved vegetables. 
After having been burned, and the ash dissolved in an appropriate acid, a 
solution is obtained, which is made up toa definite,volume. 50 c.c. is treated 
with a fixed excess of ammonium hydrate in a “Nessler” glass. , The same 
amount of ammonia is added to 50 c.c. of water in another glass, and a very 
weak standard solution of cupric sulphate is dropped in from a burette until 
the colors match, and the amount of copper solution used is noted and 
calculated. Small quantities of ferric iron may also be estimated in the same 
way by the use of potassium ferrocyanide in the presence of a fixed amount of 
acidulation with hydrochloric acid, and matching the color by a weak stan- 
dard solution of ferric chloride. This is often useful in analysing bread for 
the presence of alum, when we first weigh the precipitate of aluminium phosphate 
containing some ferric phosphate, then dissolve it in HCl, find the amount 
of iron present in this manner, and deduct it, so saving a long separation. 


130 VOLUMETRIC QUANTITATIVE ANALYSIS. 


XV. TABLE OF COEFFICIENTS REQUIRED IN THE VOLUMETRIC 
ANALYSIS DESCRIBED IN THIS CHAPTER. 


Standard Acid Solution. 


Oxalic acid 
Ss geen acid 
NH, 


NH, Oe ; 
NH “HCO, - NH .NH,CO, A 
Nab, O, . 10H, O ; : 
Pb(C, H,0 333H.0 + 

Pb, 20(C3H302)3 ‘ . 
Ca2HO . = F . 
CaO 4 ; : a 5 
Caco, . ; : : 
Ba(HO), : 
Ba(HO),8H,O0 


C0, 


K.C,H,O, (converted into © K,C05) 


(KC, H,O,),H,O 
KHC H,O¢ 
receuee O, 
KC,H,0, 

K,Mn,.Og (by oxalic acid) 
KWNaC,H,0,"". : 
NaHO: . : 
Na,CO, . 
Na,CO; . ‘10H,O 
NaHCO, ‘ 
Chloral hydrate 


Standard Soda Solution. 


Sodium ie 


HC,H,O » (lacti) 
tier 0,2 : 
Chloral ie Ree 


Standard Nitrate of Silver Solution. 


Argentic nitrate 
CN : 


HCN 
KCN 
NG! 
1G | 
NaCl 
KBr 
NaBr 
Cis. 


‘O17 
0052 
"0054. 
"01302 
00535 
"00745 
700585 
"O1I9 
‘0103 


"00355 | 





Standard Iodine Solution. coerrr, 


Iodine . ; : ; : ; *#OL27 
SO, ; 5 ; : : 0032 
H,SO, , ; : 4 : . ‘OO4I 
As,O, ; ; : : - *00495 
Na,S,0,5H,O. : : : . 0248 
Na,SO,7H,O . F . - . "0126 
K,SO,2H,O . . ; ; 2:0 "G07 
Standard Bichromate of Potassium. 
Potassium bichromate . ‘ « “O1475 
Fe(Ferrous) . : ; : . *o168 
FeSO, . : : ; : . 70456 
FeSO0,20,0 ; : : - *0564 
FeSO,7H,O . : ; ; . 10834 
Fe,(AsO,). = ; é ; . 70446 
Fe,(PO,)s ; , : hs . *0358 
EReCOp ax ; : : : - *0348 
FeO. 5 : ; b . 10696 
FeO : F ‘0216 
Standard By soil Stes Solution. 
Hyposulphite of sodium . : . *0248 
Logs : A : ; : = OEay 
i hae : : : ; : ~ 700355 
Br: : ? 5 : : . ‘0080 


Standard Barium Chloride Solution. 


Barium chloride Bee : . ‘104 
BaCl,2H,O° 5 : eae > | 
H,SO, ° . . . . e *049 
SO, ‘ . : he . *048 
SO, ‘ R 4 . : - ‘O40 
Standard Permanganate of Potassium. 
Potassium permanganate 4 . *00316 
Fe(ous) ; ‘ : 0056 
FeSO, O152 
FeSO, . 7H,O. 0278 
FeCO, : o116 
FeO : ‘ : 1" OOF2 
H,C,0,2H,0 . ; F : » 4 (O0RS 
CeC.Q, . 9H,O : : ae 


Standard Fehling’s Solution. 
(10 c.c. used.) 


Glucose : : pens 
‘Cane sugar (after inversion) : . °0475 
Maltose . . : : . ‘082 
Lactose . - Rargir et | 
Starch (after conversion) ; - °045 
Nitrometer Analysis. 
‘00281 HNO, 
700241 N,O 
Each a of NO 00450 KNO, 
equals gra 00334 CaH,..NO, 
70026 Urea 
Eachcc. of CO, at N.T.P. (0042 (NH,)2CO; 
equals gramme of "001967 CO, 


Cl AP a BE Real bk 


GRAVIMETRIC QUANTITATIVE ANALYSIS OF METALS 
BINA ILS. 


DIVISION I, PRELIMINARY REMARKS. 


GRAVIMETRIC quantitative analysis is that method by which the substance to 
be estimated is converted into some chemically definite compound, weighed as 
such, and the amount of the original substance obtained from this weight by 
calculation. ‘The same definite compound will answer both for the estimation 
of its metal and of its acid. For example, if we precipitate a known weight of 
argentic nitrate with hydrochloric acid we obtain insoluble argentic chloride, 
which may be filtered out and weighed, and the amount (x%) of Ag in the 
quantity started with calculated therefrom, because,— 


AgCl : Ag :: weight of AgCl found : x. 
Tro 5): 105 :.: re Hp EAL Rages 


If, on the other hand, we start with a known weight of hydrochloric acid, 
precipitate it with argentic nitrate, and collect and weigh the argentic chloride 
formed, we can find the amount (%) of real HCl actually present in quantity 
started with, because,— 


AgCl : HCl :: weight of AgCl found : x. 
Tana On Ge. it ‘ “ ieeek Saks 


Before giving the individual processes for the quantitative estimation of the 
various metals, we must first say something about the preparation of filters, 
and the washing, drying, and weighing of precipitates, which will serve as. 
general directions and so save continual repetition of details. 


(A) The Preparation of Filters. 


Ready-cut filters may be procured from the dealers in chemical apparatus. 
The kind known as Swedish is the best for all cases where the precipitate is 
finely divided or pulverulent. For gelatinous precipitates, such as ferric hydrate 
and calcium phosphate, the white English filters are preferable; but they 
should never be used, say, for barium sulphate or calcium oxalate, as those 
bodies would very likely pass through the pores of the filter, and so cause a 
loss in the analysis. ‘The only drawback to Swedish papers is their filtering 
rather slowly. Whatever paper be used, the size for quantitative operations is, 
for the larger sort, six inches in diameter, for the smaller, about two inches. 
The small sort is used where we have to deal with traces of precipitate only, 
or when a small quantity of fluid has to be filtered. The paper should yield 
nothing to dilute acids, and if the ash exceed one milligramme per large filter 
it will in most cases be remedied by placing, say, 100 cut filters for some 


132 QUANTITATIVE ANALYSIS OF METALS. 





hours in a basin filled with a mixture of one volume of HCl and eight volumes 
of water. They must then be repeatedly washed with distilled water till quite 
free from acidity, otherwise they would crumble to pieces when being folded. 
The washing is a very tedious operation indeed, and having been completed, 
the basin is put on to a water bath till the filters are perfectly dry. 


(B) Estimation of the Ash of Filters. 


This is most conveniently done by folding ten filters in a small compass, 
twisting a long platinum wire round the packet so as to form a cage, holding 
the free end in the hand and the paper over a previously weighed platinum 
crucible, while touching it with the flame of a Bunsen burner. The paper 
burns and the ash drops into the crucible, while any particles of carbon which 
have escaped combustion are quite consumed by exposing the crucible for 
some time to a red heat till the ash gets perfectly white. The crucible after 
cooling is reweighed, and its increase is the ash of ten filters. Divided by 10, 
we get the ash of one filter ; and in every case where both filter and precipitate 
are burned, the ash of the filter thus found must always be deducted from 
their total weight, and the difference is then the actual weight of the 
precipitate. 


(C) The Collection and Washing of Precipitates. 


When the precipitate has been fully formed and the supernatant fluid has 
become quite clear, the latter is poured on the filter (which is either previously 
> tared or not according to circumstances), care being taken not 
to disturb the precipitate. ‘This is done by holding a glass rod 
in a perpendicular position over the filter, placing the lip of the 
beaker against it, and causing the liquid to flow steadily down 
the rod into the filter. When the latter is three-fourths full, the 
beaker is turned into an erect position and the rod drained 
against the inside of the lip, and then laid across the top of the 
beaker until it is time to refill the filter. After thus pouring off 
as much as practicable, the precipitate remaining in the beaker 
is treated with water and well stirred. When the whole has once 
more settled, the clear fluid is again passed through the filter. 
Fig.30. | This operation having been repeated three or four times, the 
precipitate is allowed to pass on to the filter, any particles which stick to 
the sides of the beaker being removed with a feather, or a rod tipped with a 
small piece of black india-rubber tubing ; and the whole having been thus 
collected, the washing is continued by means of a washing-bottle (fig. 30), till 
the precipitate is quite freed from its soluble impurities. For instance, in 
estimating sulphuric acid, the barium sulphate is washed till the filtrate no 
longer gives a turbidity with argentic nitrate. 

Many bodies, as ferric and aluminic hydrate, most phosphates, barium sul- 
phate, and some of the carbonates, are best washed with boiling water. Others, 
on the contrary, must be washed with cold water,—such as plumbic sulphate, 
for which we use cold water acidified with some H,SO4; magnesium 
ammonium phosphate, for which cold dilute ammonium hydrate is used, etc. 





(D) Drying of Precipitates. 


After the precipitate has been thoroughly washed and perfectly drained, the 
funnel containing it is loosely covered over with filter paper and then put into 
the water oven or air bath till dry. Most precipitates are dried at a temperature 
of 100°C. (212° F.), but some of them require a heat of 105° C. (220° F.) before 


PRELIMINARY REMARKS. 133 





becoming constant in weight. Prolonged and repeated drying is only necessary 
when the precipitate is weighed on the filter, as described below. Fig. 31 
shows a water oven for drying at 212° F., while fig. 32 shows an air bath for 
drying at higher temperatures. This bath is fitted with an apparatus for 
automatically controlling the gas supply, and consequently the temperature. 


ss 
= aN i} 





Fig. 31. Fig. 32. 
(Z) Igniting and Weighing Precipitates. 

Most precipitates must first be ignited before they can be weighed. This 
is to drive off water, which they may still retain after drying at 212° F., or 
carbonic anhydride and water. For instance, zinc is best weighed as oxide, 
and therefore the precipitate, consisting of oxycarbonate, is first ignited. Iron 
is precipitated as hydrate, but the composition of that body not being;constant, 
it is ignited and so made into pure oxide before weighing. As soon, therefore, 
as the precipitate appears dry, it is carefully detached from the filter and 
put into a previously ignited and weighed crucible, the filter is burned on the 
lid (which has been weighed together with the crucible), the ash is thrown into 
the crucible, and the latter covered with the lid. The crucible is now sup- 
ported by a pipe-clay triangle, and gently ignited at first, to prevent spurting 
from the sudden evolution of steam or other gases. The lid is now taken 
off, and the crucible inclined a little, so as to give a free access Oia meune 
ignition is continued for some minutes, and the crucible, having been again 
covered with the lid, is allowed to cool and weighed. For accurate estima- 
tions it is best to let it cool under a desiccator. Such an arrangement is 
shown in fig. 33, in which is a vessel containing strong sulphuric acid to 
keep the air under the glass shade always free from moisture. 





Fig. 33. Fig. 34. 

The heat of an ordinary Bunsen burner is generally sufficient for all pur- 
poses; but the conversion of calcium carbonate into oxide requires the aid of 
a gas blowpipe ; while argentic chloride must be heated with a rose Bunsen 
or spirit lamp until it just begins to fuse. ‘The filters are, as already shown, 
burned separately, to prevent any reduction of the precipitate by the carbon 
of the filter. 

Some precipitates are not ignited, but weighed on a previously tared filter. 
Before weighing the filter—for which purpose a weighing tube (fig. 34) is used, 


134 QUANTITATIVE ANALYSIS OF METALS. 


or the filter is placed between two closely-fitting watch-glasses provided with a 
clamp to hold them together—it must first be dried for fifteen minutes at 
212° F. After drying the precipitate, the filter is again placed in the tube or 
between the glasses and reweighed: the increase shows, of course, the weight 
of the substance. It is well to replace the filter in the bath for, say, half an 
hour, and to weigh again. Should the weight be considerably less, it must be 
once more put into the bath and reweighed. Another method of weighing 
precipitates on a filter is to prepare two filters of equal size, Aand B. Cut off 
the bottom point of B, so that a will go inside it with its point projecting 
through the opening. Now put B on the weight scale of the balance, and cut 
off minute slices from the top of a until the two are exactly counterbalanced. 
Place a inside B, and then, having put both in the funnel, collect the preci- 
pitate, wash, and dry as usual, and cool under the desiccator. Lastly, detach 
B, and use it for a tare, putting it into the weight pan, and then the weights 
required to balance a and its contents will be the weight of the precipitate, 
because, both filters having been exposed to the same conditions, the tare is 
accurate. 


(/) Estimation of Moisture. 


A watch-glass is exactly tared on the balance, and then 2 grammes of the 
substance (in powder, if possible) are carefully weighed upon the glass, and 
the total weight noted. ‘The glass, with contents, is then placed in the drying 
oven and heated therein for an hour, at the expiration of which it is removed 
to the desiccator, and, when cold, is weighed and the weight noted. It is 
then replaced in the oven for half an hour, and the cooling and weighing 
repeated. If the two weights do not agree within, say, 2 milligrammes, the 
process is repeated until two concordant weighings are obtained. The weight 
after drying deducted from the total weight of glass + substance started with 
gives the moisture, which figure multiplied by 50 gives percentage. 


(G) Estimation of the Ash of Organic Bodies. 


This determination is necessary in every analysis of a vegetable or animal 
substance. A platinum dish is heated to redness, cooled under the desiccator, 
weighed, and the weight noted. A suitable quantity, say 5 to 10 grammes of 
the substance, is weighed into the dish, which is then arranged on a triangle 
support over a Bunsen burner and heated to dull redness. If after fumes 
cease the substance is seen to have assumed a coke-like form, it is removed 
from the dish into a small dry mortar, and having been carefully powdered, 
the powder is replaced in the dish and maintained at a dull red heat until it 
has become perfectly white, or at least until all carbon has been burned off. 
If the burning proves very tedious and the last traces of carbon are very 
difficult to burn, the addition of a light sprinkling of ammonium nitrate will 
cause the process to complete itself more rapidly. The dish is now cooled 
under the desiccator and weighed, and the weight of the empty dish having 
been deducted, the difference gives the weight of the ash, which is then cal- 
culated to percentage. The heat should not be allowed to rise to bright 
redness, because potassium and sodium chlorides, which are very common 


constituents of the ash, would be thereby volatilised to some extent and so 
lost. 


(4) Analytical Factors for Calculating the Results of Analyses. 


To save the working out of a rule of three sum on the result of each 
analysis it is customary to employ factors. These are obtained by dividing 
the weight of the required body by the equivalent weight of the form in 


ESTIMATION OF SILVER AND LEAD. 135 


a eee nr Enea 


which it is precipitated. Thus, supposing we are estimating the amount of 
argentic nitrate present in a solution containing ‘6 gramme of the salt, and 
have precipitated and weighed the same in the form of argentic chloride, we 
have :— 

Molecular weight of AgNO; 170 

Equivalent weight of AgCl 143°5 
It now only remains to multiply this factor by the weight of the precipitate 
to obtain the answer. Let us further suppose that the weight of the precip1- 
tate was *5 gramme, then 1°1847 X °5 = '59235 real AgNO, present in the 


: x 
‘6 gramme taken; then 99233 = 98°73 per cent. real AgNO; present 


= 1'1847, analytical factor. 


in the sample. 


DIVISION Il. GRAVIMETRIC ESTIMATION OF METALS. 
1. ESTIMATION OF SILVER. 
(A) As Argentic Chloride. 
(Practise upon *5 gramme pure AgNO; dissolved in 100 c.c. H,O.) 


Silver is most conveniently weighed as chloride, because this body is per- 
fectly insoluble in water and dilute acids, and separates readily. ‘The silver 
solution to be estimated is acidified with nitric acid, and hydrochloric acid is 
dropped in until no more precipitate forms. It is best to have the solution 
warm, and to stir till the supernatant liquid has got perfectly clear. ‘The clear 
fluid is now poured off through a filter, and the chloride is washed by decan- 
tation with boiling water (always pouring the washings through the filter) till 
every trace of acid is removed, and subsequently the whole precipitate is 
brought upon the filter. The filter and contents are then dried in the water 
oven, and the chloride transferred into a weighed porcelain crucible, and 
heated over a low flame till it just commences to fuse. The filter is burned 
on the crucible lid, and the ash treated with a drop of aqua regia, the result- 
ing chloride dried, the lid placed upon the crucible, and the whole weighed. 
The tare of the crucible and lid having been deducted, the balance is AgCl, 
from the quantity weighed out for analysis. 


: (B) As Metal. 
(a) In organic salts, by igniting a weighed quantity of the salt in a tared 
porcelain crucible, and weighing the ash, which will consist of pure metallic 


Suver. ,:. 

(6) In alloys, by cupellation, as follows :—The weighed alloy is wrapped in 
lead foil, placed on a little cup or cupel made of bone ash, and heated to 
bright redness in a muffle furnace. The lead oxidises and sinks into the 
cupel, carrying the impurities with it, and leaving a button of pure silver, 
which is cooled and weighed. 


2, ESTIMATION OF LEAD. 
(A) As Plumbic Oxide. 
(Practise upon *5 gramme pure plumbic acetate.) 


The solution containing the substance to be analysed is precipitated with 
ammonium carbonate in the presence of a little ammonium hydrate. The 


136 QUANTITATIVE ANALYSIS OF METALS. 





precipitated plumbic carbonate is then collected on a small filter, washed, and 
dried. ‘The dry precipitate is removed as completely as possible from the 
filter-paper, and introduced into a weighed porcelain crucible. The filter 
having been burned on the lid, and its ash added to the contents of the 
crucible, the whole is ignited, cooled, and weighed. By ignition, the oxide 
is formed ; and after deducting the weight of the crucible, the balance is PbO, 
from the quantity weighed out for analysis. Organic salts of lead require 
simply to be ignited in a tared porcelain crucible, with free access of air, 
adding a sprinkling of ammonium nitrate (to prevent reduction to the metallic 
state), and weighing the resulting PbO. 


(2) As Plumbic Chromate. 


(Practise upon ‘5 gramme of plumbic nitrate.) 


The solution is mixed with excess of sodium acetate and precipitated with 
potassium chromate. The precipitate is collected, washed with water, acidu- 
lated with acetic acid, dried, and ignited in a platinum crucible with the usual 
precautions. ‘The filter is burned on the lid, treated with a drop or two of 
nitric acid, dried, and again ignited. The crucible and contents are weighed, 
and the tare of the crucible having been deducted, the balance is PbCrO,, from 
the quantity weighed out for analysis. 

Lead may also be precipitated as PbSO,, dried, ignited, and weighed as such. 


3, ESTIMATION OF MERCURY. 


(A) As Metal. 
(Practise upon 1 gramme of “white precipitate,” which should yield 77°5 % Hg.) 


Take a combustion tube of hard glass closed at one end, and put in: (1) a 
little magnesite—MgCoOs ; (2) the white precipitate mixed with excess of quick- 
lime ; (3) a few inches of quicklime; (4) a loose plug of asbestos. Draw out 
the open end of the tube before the blowpipe and bend it down at a right angle. 
Give the tube a tap or two on the table to insure a free passage along the upper 
part for gases, and place it in a combustion furnace, with its open end dipping 
under the surface of some water in a small flask. Apply heat to the front part 
of the tube, and go gradually backwards until the whole is heated to redness 
and the CO,, given off by the MgCOs, has swept all the mercury vapor out of 
the tube. The mercury collects as a globule under the water in the basin, and 
is transferred to a tared watch-glass, perfectly dried by pressure with blotting- 
paper, and weighed. ee 


(G) As Mercuric Sulphide. 
(Practise upon ‘5 gramme of mercuric chloride.) 


Through the solution of the mercuric salt a current of H,S is passed till 
the liquid is saturated. The precipitate is collected on a weighed filter, 
washed first with water, then with absolute alcohol, and finally, to remove 
any free sulphur, with a mixture of equal parts of ether and carbon disulphide. 
After drying at 212° F. and weighing, the balance is HgS from the quantity 
weighed out for analysis. 


ESTIMATION OF CADMIUM, COPPER, AND BISMUTH. 137 





4, ESTIMATION OF CADMIUM. 
(Practise upon ‘5 gramme of CdCO; dissolved in diluted HCl.) 
As Sulphide. 


The solution is precipitated with ammonium hydrate and ammonium sul- 
phide. The cadmium sulphide is collected in a weighed filter, washed, dried 
at 212° F., and weighed as CdS. In the presence of metals of the fourth 
group the solution must be slightly acidified with hydrochloric acid and 
precipitated by a current of sulphuretted hydrogen. 


5. ESTIMATION OF COPPER. 
(A) As Cupric Oxide. 
(Practise upon *5 gramme of pure CuSO . 5H,0.) 


The solution is boiled with a slight excess of sodium hydrate. The 
precipitate is filtered out, washed, and dried. It is then carefully removed 
from the paper to a weighed crucible, and the filter having been burned on 
the lid and the ash added to the contents of the crucible, the whole is well 
ignited, cooled in a desiccator, and weighed rapidly, because cupric oxide is 
very hygroscopic. To make sure that the oxide contains no cuprous oxide, it 
is moistened with a little fuming nitric acid, dried with the lid on, ignited 
for ten minutes, and then weighed as CuO. This operation requires care, 
being liable to involve loss by spurting. 


(B) As Metallic Copper. 


The solution, which must be free from other metals precipitable by electro- 
lysis, is introduced into a weighed and very clean platinum basin. It must 
contain a slight excess of sulphuric acid, but on no account nitric acid. The 
dish is then attached to the wire from the zinc plate of a galvanic cell, thus. 
becoming the cathode. The other wire is connected toa piece of platinum 
wire to form an azode, and this latter is then immersed in the liquid. Aftera 
short time the fluid will become quite colorless, and the basin will be coated 
with metallic copper. The fluid is now poured off, and the copper repeatedly 
washed with boiling water till all acidity is removed. The basin is finally 
rinsed with absolute alcohol, quickly dried, weighed, and the tare of the basin. 
having been deducted, the difference is metallic copper in the quantity 
weighed out for analysis. 

The use of a battery may be dispensed with, and a fragment of pure zinc: 
used to precipitate the copper, with sufficient acid to dissolve all the zinc 


before pouring off. 


6. ESTIMATION OF BISMUTH. 
(A) As Bismuth Sulphide. 
(Practise upon *75 gramme of dismuthi et ammonia citras B.P.) 


This process (although employed in the B.P.) cannot be much recom- 
mended, as the sulphide is apt to increase in weight on drying, owing to the 
absorption of oxygen. A current of sulphuretted hydrogen is passed through 
the acid bismuth solutioh ; the resulting sulphide is collected on a tared filter, 
dried at 212 F., and weighed as Bi,S3. : 


138 QUANTITATIVE ANALYSIS OF METALS. 


(4) As Bismuth Oxide. 


The solution for analysis is diluted with water, and precipitated with a 
slight excess of ammonium carbonate. The precipitated bismuthous oxy- 
carbonate is collected, washed, and dried. It is then separated from the filter 
paper, and the latter having been burned on the lid of a weighed crucible, 
the whole is introduced into the crucible, and ignited, cooled, and weighed as 


7. ESTIMATION OF GOLD. 
As Metallic Gold, by Cupellation. 


The alloy containing the gold is treated exactly as described under silver. 
The resulting metallic button is rolled out into a flat foil, and is then digested 
with nitric acid, which dissolves any silver, and the resulting gold is re-fused 
into a button and weighed. 


8. ESTIMATION OF PLATINUM. 
As Metallic Platinum. 


The solution, which must contain the platinum as chloride, is concentrated 
and precipitated with excess of ammonium chloride. ‘The precipitate is well 
washed with spirit of wine, dried, ignited, and weighed as metallic platinum. 


9. ESTIMATION OF TIN. 
(A) As Stannic Oxide. 


Alloys containing tin, but free from antimony or arsenic, are treated with 
nitric acid, which converts the tin into oxide and other metals into nitrates. 
The acid fluid is evaporated nearly to dryness, the residue taken up with 
water and a little nitric acid; the oxide is washed by decantation, collected 
on a filter, completely washed and dried. It is then ascompletely as possible 
detached from the filter, the latter is burned on a lid, the ash added to the 
contents of the crucible, and the whole ignited. After cooling, the oxide is 
moistened with a little nitric acid, dried (with the lid on), again ignited, and 
weighed as SnQg,. 

Where we have to deal with tin in solution, the following method is 
applied :— 

The solution, which must be free from metals of the first three groups, is 
precipitated with sulphuretted hydrogen, the resulting sulphide is washed with 
- solution of ammonium acetate, which will prevent the stannic sulphide from 
passing through the filter. ‘The sulphide is transferred to a weighed crucible, 
and the whole ignited, at frst very gently, until fumes of sulphurous anhydride 
cease, and then at a very high temperature, with the addition of a fragment of 
ammonium carbonate. 

This process depends on the conversion of the sulphide into SnO, by 
ignition; but it must be conducted with care, as a too rapid application of 
heat would cause the change to take place suddenly, and some of the sulphide 
would be lost. , 


(2) As Metallic Tin. 


This process, which is only applicable to tin stone, consists in fusing a 
known quantity of the pulverised ore with potassium cyanide in a porcelain 
crucible, when a small button or granules of metallic tin will be obtained on 
treating the mass with water. The tin is washed, dried, and weighed. 


ESTIMATION OF ANTIMONY, ARSENIC, AND COBALT. 139 





10. ESTIMATION OF ANTIMONY. 


As Antimonious Sulphide, with or without Subsequent Conversion into 
Antimonius Antimonic Oxide. 


(Practise upon ‘5 gramme of “ tartar emetic.”) 


The acid solution is mixed with tartaric acid, to prevent the precipitation of 
an oxysalt, diluted with water, and precipitated with sulphuretted hydrogen, 
the sulphide collected on a weighed filter, dried at 220 F., and weighed. 
The conversion of the sulphide into oxide is best done by igniting an aliquot 
part in a porcelain crucible, with excess of mercuric oxide, and finally igniting 
very strongly. The remaining Sb,O, is then weighed. The B.P. simply 
moistens and warms the sulphide with nitric acid till red fumes cease, and 
then dries, ignites, and weighs as Sb,O,. 


11. ESTIMATION OF ARSENIC. 
(A) As Arsenious Sulphide. 


(Practise upon *5 gramme As,QO3.) 


The solution must contain the arsenic as arsenious acid. After adding 
some HCl, a current of sulphuretted hydrogen is passed through the liquid 
till the latter acquires a strong smell. The excess of gas is now removed by 
warming the fluid and passing a current of carbonic anhydride through it. 
The sulphide is collected on a weighed filter, washed, dried at 212° F., and 
weighed as As,S3. 


(B) As Magnesium Ammonium Arseniate. 


If the substance be arsenious acid it is dissolved in some hot solution of 
sodium carbonate, excess of hydrochloric acid is added, and the fluid mixed 
with excess of bromine water. Arsenic and sulphur compounds, on the other 
hand, are dissolved in hot potassium hydrate and treated with excess of 
chlorine gas to convert them into arsenic acid. The solution of arsenic acid 
thus obtained by either of the foregoing methods is mixed with large excess 
of ammonium hydrate, and, after being allowed to cool, precipitated with 
magnesia mixture. After standing for at least twelve hours, the precipitate 
is collected on a weighed filter, washed with a mixture of one volume of 
ammonium hydrate and three volumes of water till free from chlorine, dried 
for three hours at 220° F., and weighed as MgNH,AsO, 


12, ESTIMATION OF COBALT. 
As Potassium Cobaltous Nitrite. 


The solution is concentrated to a small bulk, the excess of acid is neutralised 
with potash, and excess of potassium nitrite and a little acetic acid (to keep 
the solution slightly acid to test-paper) are then added. After the lapse of 
twenty-four hours all the cobalt will have crystallised out as potassium cobaltous 
nitrite. This salt is quite insoluble in the mother liquor, but slightly so in 
pure water. For the washing, a 10% solution of potassium acetate is used, 
wherein the salt is also insoluble, and the acetate is afterwards removed by 
washing with alcohol. A weighed filter is used and the precipitate dried at 
Cay ae 


140 QUANTITATIVE ANALYSIS OF METALS. 





13. ESTIMATION OF NICKEL. 
As Metal. 


The solution is precipitated with excess of sodium hydrate and boiled. 
The precipitate is washed with boiling water, dried, ignited, and weighed. 
The ignited residue, or a known portion of it, is now introduced into a 
weighed porcelain boat, and reduced at red heat by a current of hydrogen. 
The reduced metallic nickel is afterwards weighed. 


14. ESTIMATION OF MANGANESE. 
As Maganoso-manganic Oxide. 
(Practise upon ‘75 gramme of pure MnSO, . 7H,0.) 


The solution for analysis, if strongly acid, is neutralised with ammonium 
hydrate and precipitated by ammonium sulphide. The precipitated manganous 
sulphide is washed with water containing ammonium sulphide, and dissolved 
in hydrochloric acid. Excess of sodium acetate is then added, and chlorine 
gas is passed through the liquid until all the manganese precipitates as 
manganic peroxide, which is then collected, washed, and calcined in a 
weighed crucible to bright redness. This forms Mn;O ; the crucible with 
the contents is then cooled and weighed. 


15. ESTIMATION OF ZINC. 
As Zine Oxide. 
(Practise upon *75 gramme of pure ZnSO . 7H,0.) 


The solution of the zinc salt is precipitated boiling with sodium carbonate, 
and the solution boiled well. The precipitate is allowed to settle, washed 
by decantation with boiling water, filtered out, and dried. It is then 
introduced into a weighed crucible, ignited for some time at a bright red 
heat, cooled, and weighed. The ignition changes the precipitated zinc 
carbonate to oxide, and it is weighed as ZnO. Or the solution is precipitated 
with ammonium sulphide, the zinc sulphide collected on a filter, washed with 
dilute ammonium sulphide, dried, ignited, and finally weighed as oxide. This 
latter method is useful when only small quantities of zinc are present. 


16. ESTIMATION OF IRON. 
As Ferric Oxide. 
(Practise upon ‘75 gramme of pure FeSO, . 7H,0O.) fe 

The solution is boiled with a nitro-hydrochloric acid, to insure that the whole 
of the iron is in the ferric state. Excess of ammonium hydrate is added, 
the whole boiled, and rapidly filtered. The precipitated ferric hydrate is 
washed with boiling water, dried, and ignited in a weighed crucible for some 
time. 

In the presence of organic matter, such as citric or tartaric acids, the iron 
must first be separated by precipitation with ammonium sulphide, the precipi- 
tate washed with dilute ammonium sulphide, redissolved in hydrochloric acid, 
boiled, oxidised by potassium chlorate, and then precipitated with ammonium 
hydrate, as directed. In the presence of manganese the solution should be 


ESTIMATION OF ALUMINIUM AND CALCIUM. I4I 





nearly neutralised by ammonium hydrate and then boiled with excess of 
ammonium acetate, and the resulting ferric oxy-acetate collected, washed, 
dried, and ignited to Fe,O3. 


17. ESTIMATION OF ALUMINIUM. 
As Aluminic Oxide. 
(Practise upon 1 gramme of pure alum.) 


The solution containing the alum or other salt of the metal is precipitated 
with a slight excess of ammonium hydrate, and boiled until it only smells 
very faintly of ammonia. The precipitated aluminic hydrate thus obtained 
is filtered out, washed with boiling water, and dried. The dry filter and 
its contents are transferred to a weighed platinum crucible, and ignited to 
bright redness for some time, allowed to cool, and weighed as Al,O;, 


18. ESTIMATION OF CHROMIUM. 
As Chromic Oxide. 


Salts of chromium are at once precipitated with ammonium hydrate, and the 
precipitate washed, dried, ignited, and weighed as Cr,O3. Soluble chromates 
are first reduced by means of hydrochloric and sulphurous acids (or, instead 
of the latter, spirit of wine may be used), and the chromium precipitated as 
hydrate by ammonium hydrate ignited and weighed as Cr,O,, all as described 
above for aluminium. 


19. ESTIMATION OF BARIUM. 
As Barium Sulphate, 
(Practise upon ‘5 gramme of BaCl, . 2H,0.) 


To a solution in boiling water add excess of sulphuric acid, boil rapidly for 
a few minutes, and set aside to settle. 

The clear liquor is poured off as closely as possible, and the precipitate 
collected on a filter of Swedish paper, and washed with boiling water. The 
filter and precipitate are next dried and ignited in a weighed platinum crucible 
(the precipitate being removed as perfectly as possible from the paper, and 
the latter first burned separately on the crucible lid, and the ash added to the 
contents of the crucible, to avoid the reduction of BaSO, to BaS by the carbon 
of the paper). The crucible and its contents having been weighed, and the 
weight of the crucible deducted, the difference equals the BaSO,. 


20. ESTIMATION OF CALCIUM. 
As Calcium Carbonate. 
(Practise upon ‘5 gramme of powdered calc-spar dissolved in dilute HCl.) 


The solution of the lime salt is mixed with ammonium chloride, and is then 
made alkaline by ammonium hydrate. Should any precipitate (for instance, 
calcium phosphate) form, it is redissolved by means of acetic acid, and any 
insoluble residue is removed by filtration. Ammonium oxalate is now added 
in excess. The precipitated calcium oxalate is boiled for a few minutes, 

filtered, the precipitate washed until free from chlorides, and the filter and 


142 QUANTITATIVE ANALYSIS OF METALS. 





contents dried at 212° F. The precipitate is now carefully transferred to 
a tared platinum crucible and gently ignited. It is then moistened with a 
solution of pure ammonium carbonate, evaporated to dryness, heated until 
no more fumes are evolved, and then weighed as CaCOs. 


21. ESTIMATION OF MAGNESIUM. 
As Magnesium Pyrophosphate. 
(Practise upon ‘5 gramme of pure MgSO, . 7H,0.) 


The solution, which must be strong, is mixed with some ammonium 
chloride, and then with one-third of its bulk of ammonium hydrate, entirely 
cooled, excess of di-sodium hydrogen phosphate added, and the whole set 
aside for some hours. Care must be taken not to touch the sides of the 
beaker with the stirring rod, as otherwise particles of the triple phosphate 
will adhere to them so tenaciously that they can only be removed with great 
difficulty. The precipitate is collected on the filter and washed with a 
mixture of one volume of ammonium hydrate and three volumes of water, 
till the washings are free from chlorine, and dried. The precipitate is now 
detached from the filter and put into a weighed platinum crucible, the filter 
is burned in the lid, the ash added to the contents of the crucible, and the 
whole strongly ignited and weighed as Mg,P.O;. 

It sometimes happens that the phosphate, even after prolonged ignition, is 
very black. In that case it is, after cooling, thoroughly moistened with nitric 
acid, carefully dried, and re-ignited, when it will be found to be perfectly 
white. ' 

The B.P. estimates magnesium in MgSO, by simply precipitating a boiling 
solution with Na,COs, and collecting, drying, igniting, and weighing as MgO. 


22. ESTIMATION OF POTASSIUM. 
As Potassium Platino-Chloride. 
(To be practised upon ‘2 gramme of pure KCl.) 


The solution is placed in a small porcelain basin, and mixed with a good 
excess of solution of platinic chloride. The whole is evaporated to dryness 
on a water bath kept at a temperature of about 200° F. When quite dry it is 
again digested with a few drops of platinic chloride solution, and taken up with 
alcohol. ‘The precipitate is collected on a weighed filter, washed with alcohol 
till the washings appear quite colorless, dried at 212°F., and weighed as 
PiCl, . 2KCIL 


23. ESTIMATION OF SODIUM. 
As Sodium Sulphate. 
(Practise upon ‘5 gramme of pure NaCl.) 


This method is applicable where we have to deal with a sodium salt con- 
taining a volatile acid. The solution is mixed with excess of sulphuric acid 
and evaporated in a weighed platinum basin. When fumes of sulphuric acid. 
become visible, the basin is covered over with a lid or foil which has been 
weighed together with the crucible, and gradually heated till fumes cease. 
While red-hot the foil is lifted up a little, and a small lump of ammonium 


ESTIMATION OF POTASSIUM AND AMMONIUM. 143, 





carbonate put in the crucible, which operation is repeated after a few minutes, 
and the residual Na,SO, is cooled and weighed. The object of introducing 
the ammonium carbonate is to remove the last traces of free sulphuric acid. 


24, ESTIMATION OF POTASSIUM AND SODIUM IN PRESENCE OF 
METALS OF FOURTH GROUP. 


(Practise upon the residue left on evaporating 1 litre of ordinary drinking- 
water, and redissolved in a little dilute HCl.) 


The solution is first of all precipitated with excess of barium chloride, 
which throws down sulphuric, phosphoric, etc., acids. Barium hydrate (or 
some milk of lime) is now added in slight excess, when any magnesia will 
also be thrown down. To the filtered liquid excess of ammonium carbonate 
is added, the precipitate is filtered out, and the fluid evaporated to dryness in 
a platinum crucible on the water bath. When quite dry, it is gently heated 
as long as white ammoniacal fumes are visible. ‘The residue, which will now 
consist of alkaline chlorides, is however not quite fit for weighing, and must 
be purified. This is done by redissolving in water and adding a little 
ammonium carbonate, when a slight precipitate will form. After filtering, 
the fluid is evaporated (this time in a tared platinum basin) on the water 
bath, and when dry the residue is gently heated to faint redness for a minute, 
cooled, and weighed. When no sodium is present it will now be pure 
potassium chloride; but should it also contain sodium chloride, it must be 
redissolved, the potassium estimated by PtCl, and the sodium obtained by 
difference. ‘This process is one of the most commonly occurring operations, 
because it is required in every full analysis of water, and also of the ash of 
all vegetable and animal substances, where potassium and sodium have always 
to be estimated in presence of Ca, Mg, phosphates, etc. It is therefore a 
very important one to thoroughly master. 


25. ESTIMATION OF AMMONIUM. 
As Ammonium Platino-Chloride. 


If the solution contains other basylous radicals, a known quantity of it is 
distilled with some slaked lime in a suitable apparatus, and the distillate 
received into dilute hydrochloric acid. About three-fourths is distilled over. 
The distillate is then evaporated to dryness with excess of pure platinic 
chloride (free from nitro-hydrochloric acid). The dry residue is now treated 
with a mixture of two volumes of absolute alcohol and one of ether, collected 
on a weighed filter, washed with the said ether mixture, dried at 212° F,, 
and weighed as PtCl,. 2NH,Cl. 

A less expensive method is to distil the ammonia into a known bulk o 
volumetric acid, and then check back with volumetric soda, so finding the 
amount of acid neutralised by the ammonia. 


144 QUANTITATIVE ANALYSIS OF METALS. 
oe cc oi a ad a ce 


DIVISION II GRAVIMETRIC ESTIMATION OF 
ACIDULOUS RADICALS. 


1, CHLORIDES. 
As Argentic Chloride. 
(Practise upon *5 gramme pure NaCl.) 


The solution containing the chloride is precipitated with argentic nitrate. 
Nitric acid is then added, and the whole stirred till the liquid is perfectly 
clear. The precipitate is now treated as directed (see Silver, p. 135). After 
weighing the chloride it is calculated to Cl. 


2, IODIDES. 
3, BROMIDES. 
4. CYANIDES. | 


The process for each of these is practically the same as for chloride. The 
argentic cyanide is, however, collected and weighed upon a weighed filter. 
The argentic iodide and bromide are treated like the chloride ; but 7 a filter 
is used, it must be a weighed one. The filter is afterwards reweighed, and 
the increase in weight is the amount of argentic iodide or bromide lost during 


the washing by decantation. 


5. ESTIMATION OF AN IODIDE IN THE PRESENCE OF A CHLORIDE 
AND A BROMIDE.. 


By Palladium. 


The solution, slightly acidified, is precipitated with excess of palladious 
chloride. The whole is then allowed to stand in a warm place for twenty-four 
hours, so that the precipitate may thoroughly settle. The supernatant liquor 
is poured off, and the precipitate having been collected on a filter, and 
washed, is placed in a weighed platinum crucible and ignited. The whole 
is then again weighed, and the weight, less that of the crucible, equals the 
amount of metallic palladium left after ignition, which x 2°396 = the 
amount of iodine in the weight of the sample taken for analysis. 


6. SULPHIDES. 
By Conversion into Sulphate. 
(Practise upon *5 gramme of purified “ black antimony.”) 


Are analysed by fusion with a large excess of a mixture of potassium nitrate 
and carbonate, extracting the fused mass with water, filtering, acidulating 
with hydrochloric acid, adding excess of barium chloride, and proceeding as 
for a sulphate; but calculating at the last to sulphur instead of sulphuric 
acid. Some sulphides can be dissolved in nitric acid with the addition of 
successive small crystals of potassium chlorate. Excess of hydrochloric acid 
is then added, and the whole evaporated to dryness. The mass is then boiled 
with dilute hydrochloric acid, filtered, and the filtrate precipitated with barium 
chloride as above. 


a 


SULPHA TES—NITRATES—PHOSPHATES. 145 


7. SULPHATES. 
As Barium Sulphate. 
(Practise *5 gramme of MgSO, . 7H,0.) 


.To the solution of the sulphate hydrochloric acid is added, then excess 
of barium chloride, and the whole boiled., When quite clear, a little 
more barium chloride is added, to ascertain whether all the sulphate has 


precipitated. The precipitate is now treated precisely as in the barium 
estimation. 


8. NITRATES. 
(A) In Alkaline Nitrates, 


If nitric acid be required to be estimated in, say, ordinary nitre, the sample 
must first be heated to fusion to remove moisture, and then be quickly 
powdered. A known quantity of it is now mixed in a platinum crucible with 
(exactly) four times its weight of plumbic sulphate. The mixture is ignited 
till it ceases to lose weight, and the loss will just represent the amount of 
nitric anhydride in the sample taken for analysis. 

If plumbic sulphate is used, the reaction is represented by the following 
equation :— 


PbSO, Lh 2KNO, = PbO + K,SO, ob 2NO, + O. 


(BL) By Conversion into Nitric Oxide. 
Already described at page 126. 


(C) By Conversion into Ammonia. 


The nitrate is converted into ammonia by the action of nascent Hear ee 
thus— 


HNO, + 4H, = NH, + 3H,0. 
The nascent hydrogen may be applied in various ways, as follows :— 


1. By distillation with sodium hydrate and metallic aluminium, and 
receiving the evolved ammonia into a known volume of 
standard acid. 

2. By acting on the nitrate for 12 hours with zinc or iron and dilute: 
sulphuric acid, and then adding excess of sodium hydrate, and 
distilling off the ammonia into a known volume of standard 
acid. 


In any case, the standard acid used is then volumetrically checked back by 
standard sodium hydrate, and the excess of acid used over that of alkali gives 
the amount of standard acid neutralised by the ammonia. This amount, 
having been multiplied by the strength of the acid in each c.c., is calculated. 
to ammonia. Then— 


Ammonia found xX 54 __ f amount of anhydrous nitric acid in 
17 the quantity taken for analysis. 


_ 9. PHOSPHATES. 
(A) Estimation of the Strength of Free Phosphoric Acid. 


5 grammes of the acid are evaporated in a weighed dish with 10 grammes. 
of pure litharge, and the dry residue is ignited and weighed. ‘Thus tested 
U.S.P. acid should yield 11°81 grammes of residue, and the diluted acid. 
should leave, with 5 grammes litharge, 5°36 grammes of residue. 


IO 


146 QUANTITATIVE ANALYSIS OF METALS. 





(B) As Magnesium Pyrophosphate in Alkaline Phosphates. 
(Practise upon *75 gramme of pure Na,HPO, . 12H,0.) 


They are at once precipitated with ammonium hydrate and magnesia 
mixture, and the precipitate is treated as directed under Magnesium. Should 
they contain the acid as meta- or pyro- acid, they must first either be boiled 
with strong nitric acid for one hour, or be fused with potassium sodium car- 
bonate. 


(C) As Magnesium Pyrophosphate in the Presence of Lime and Magnesia. 
(Practise upon ‘5 gramme of pure Ca,(PO,), dissolved in dilute HCl.) 


The solution (which must contain orthophosphoric acid, or, failing that, 
should be boiled with HNO; as above) is precipitated with ammonium ~ 
hydrate, the precipitate redissolved in the smallest amount of acetic acid, the 
lime precipitated with ammonium oxalate, and the phosphoric acid pre- 
cipitated in the filtrate by adding ammonium hydrate and magnesia mixture, 
and proceeding as already described for magnesium. Before precipitation this 
filtrate should be evaporated to a bulk of 3 ounces. This process is suitable 
for determining the “ soluble phosphates” in an artificial manure. 


(D) As Magnesium Pyrophosphate in the Presence of Iron and 
Aluminium. 
(Practise upon *75 gramme of B.P. Ferrz phosphas dissolved in dilute HCl.) 


The solution is mixed with excess of ammonium acetate, boiled, and ferric 
chloride added till a dark-brown precipitate forms. This is washed with 
boiling water and redissolved in a small quantity of dilute HCl. About five 
grammes (or more) of citric acid are now added, and ammonium hydrate is 
added to the whole in large excess, and, after cooling, magnesia mixture, and 
the precipitate treated as for magnesium, already described. If the addition 
of excess of NH,HO does not produce a clear lemon-yellow solution, then 
enough citric acid has not been added. | 


(Z) Estimation as Phosphomolybdate. 


If necessary, the acid solution is heated and precipitated with H,S to 
remove arsenic. The excess of H,S is boiled off, and large excess of nitric 
acid is added. An excess of ammonium molybdate and ammonium nitrate 
dissolved in nitric acid is now poured in, the liquid boiled, and finally allowed 
to stand for some hours in a warm place. The precipitate is filtered off, 
washed with dilute alcohol until free from acidity, redissolved in dilute 
ammonium hydrate, and this solution evaporated in a weighed dish on the 
water bath and dried in the water oven. Its weight + 28°5 = P.O; present. 
This process is the best for determining small amounts of total phosphates in 
cast iron, waters, and soils. 


10. ESTIMATION OF TOTAL AND SOLUBLE PHOSPHATES IN AN 
ARTIFICIAL MANURE OR OF TOTAL ONLY IN SOIL. 


(A) Total Phosphates. 


About two grammes of the finely powdered substance are weighed accurately, 
transferred to a beaker and decomposed with HCl, and where necessary with 
the addition of a drop or two of HNO;. The solution is then evaporated to 
dryness in a water bath, taken up with HCl, and after digestion the insoluble 
silicious matter is separated by filtration ; a weighed quantity of citric acid is 


ARSENIATES AND CARBONATES. 147 


added ; the solution heated up nearly to boiling point, and a weighed quantity 
of ammonium oxalate added. The quantities used must vary with the 
substance under examination, the knowledge only being acquired by ex- 
perience ; but it is seldom necessary to add more than 2 grammes citric acid 
or 2°5 grammes ammonium oxalate. The free acid is then just neutralised 
with dilute ammonia, and acetic acid added, to decidedly acid reaction. The 
liquid is kept simmering for a few minutes with constant stirring, and after 
standing a short time the calcium oxalate is filtered out. Great care must 
be observed not to have too large an excess of ammonium oxalate 
present, as magnesium oxalate in an ammoniacal solution is somewhat easily 
precipitated. ‘To the filtrate ammonia of ‘880 sp. gr. is added to about one- 
fourth of the bulk ; and to the liquid, which must remain clear, or only slowly 
throw down a small precipitate, due to the magnesia present, magnesta 
mixture is added in moderate excess. ‘The liquid must be set aside with 
occasional stirring for the precipitate to form—the time required being 
principally determined by the quantity of alumina present. It is best, 
however, to allow it to stand overnight, although in cases where the alumina 
is absent, or small, the precipitation will be found to be complete in two 
hours. The precipitate is then separated from the liquid by filtration, 
dissolved in as little HCl as possible, and reprecipitated with one-third of its 
bulk of ammonia. After allowing to.stand for two hours with occasional 
stirring, it may be filtered, and after drying converted, by ignition in a weighed 
platinum crucible, into Mg,P,O,, and weighed as such. 

The calcium oxalate is converted into CaCO, by gentle ignition, weighed, 
dissolved in HCl, and tested for P,O;, which may be present in small 
quantities, and which should be determined. 

The Mg,P,O, is calculated to Ca,(PO,), unless a full analysis is being 
made, when it is calculated to P,O;, and divided vo rata among the bases 
actually found to be in combination with it. 


(B) Soluble Phosphates. 


Five grammes of the manure are well triturated in a mortar with distilled 
water, washed into a stoppered 250 c.c. flask, and made up to the mark with 
water. After standing with occasional shaking for two hours, 100 c.c. (= 2 
grammes of sample) is drawn off by a pipette into.a beaker, 2 grammes of 
citric acid and 2°5 grammes of ammonium oxalate are dissolved in the liquid, 
which is then treated with ammonia, acetic acid, etc., as above described. If 
the amount of soluble calcium comes out low, the process should be repeated, 
using such a weighed quantity of ammonium oxalate as will just remove it 
from solution. This is because the great source of error in phosphate 
estimations is the use of excess of oxalate, causing the precipitation of 
magnesium oxalate with the magnesium ammonium phosphate. The Mg,P,0, 
is calculated to Ca,(PO,),, and reported as “ phosphate made soluble.” 


11. ARSENIATES 


are estimated precisely like phosphates; but the precipitate of ammonium 
magnesium arseniate is dried at 220° F. on a weighed filter, as already directed 
under Arsenic. The precipitate thus dried is 2(MgNH,AsO,) . H,O; or, for 
simplicity of calculation, MgNH,AsO; . $H,0. 


12. CARBONATES. 


A carbonate is estimated by the loss of weight it undergoes by the dis- 
placement of its carbonic anhydride by an acid. A small and light flask is 


148 QUANTITATIVE ANALYSIS OF METALS. 





procured, and fitted with a cork through which passes a tube (c) containing 
fragments of calcium chloride (see fig. 35). A weighed quantity of the 
carbonate is introduced into the flask with a little water, and a small test-tube 
about two inches long is filled with sulphuric acid and dropped into the 
flask, so that, being supported in an upright position, none of the acid shall 
mix with the carbonate. The cork is put in, and the weight of the whole 





apparatus having been carefully noted, it is inclined so as to allow the acid to 
run from the small tube into the body of the flask. Effervescence sets in, the 
carbonate is dissolved, and the CO,, escaping through the calcium chloride 
tube, is deprived of any moisture it might carry with it. When all action has 
ceased, and the whole has cooled, it is once more weighed. The difference 
between the two weights gives the amount of CO, evolved. 

A better apparatus is that figured (No. 36), in which c is the flask, a the 
tube to contain HCl to decompose the carbonate, and B a tube containing 
strong H,SO, through which the evolved CO, must pass, and so be perfectly 
deprived of moisture. 


18, OXALIC ACID. 


As Calcium Carbonate. 


The solution containing the acid, or its potassium or sodium salt, is made 
alkaline with ammonium hydrate, and precipitated with calcium chloride. 
The precipitate is washed till free from chlorides, dried, ignited, and finally 
weighed as carbonate. (See Estimation of Calcium.) 


14. TARTARIC ACID. 
As Calcium Oxide. 


The solution (which must contain no other bases than K, Na, or NH,) is 
made faintly alkaline by a sodium hydrate, and precipitated by excess of 
calcic chloride. The precipitate is washed, dried, ignited (with the blowpipe), 
and weighed as calcic oxide. 


15. SILICIC ACID. 
(A) In Soluble Silicates. 


By soluble silicates are meant those which are either soluble in water or 
in hydrochloric acid. The solution (which must contain some free HCl) is 
evaporated to dryness on the water bath, and the residue dried for an hour 
at 120° C. (248° F.) After cooling, the mass is moistened with strong hydro- 
chloric acid, and then boiled with water, thus leaving an insoluble residue of 
pure silica—SiO,—which is collected on a filter, washed, dried, ignited, and 
weighed. f 


QUANTITATIVE SEPARATIONS. 149 


Ie 


(B) In Insoluble Silicates. 

These bodies must be decomposed by mixing a weighed quantity of the 
finely powdered substance with four times its weight of sodium potassium 
carbonate, and fusing the whole for about half an hour. (When alkalies have 
to be estimated, a separate special fusion must be made with barium hydrate, or 
pure lime mixed with ammonium chloride, instead of the double carbonate.) The 
crucible must be well covered during fusion. After cooling, the residue is 
treated with dilute and warm HCl until effervescence ceases, evaporated to 
dryness, and treated as above described at 120° C. (248° F.), etc. 


DIVISION IV. QUANTITATIVE SEPARATIONS. 


This department is beyond the scope of the present edition. When the 
student has practised all the contents of the book up to this point, he will 
already have a sufficiently general idea of chemical analysis to enable him to 
fix the line of work he desires to make his speciality. If this be mineral 
analysis, he must pass to a larger book, such as “ Fresenius,” to complete his 
knowledge. So as to give, however, some idea of how the preceding pro- 
cesses may be joined in performing the full analysis of a mixture, we take 
the following example, because it is a standard one, and give a sketch of 
the manner of working in performing— 


The Full Analysis of the Mineral Contents of a Sample of Ordinary 
Potable Water. 

Step I. Take the total solid residue of 100 c.c. (calculated in grains per 
gallon) as directed in Chapter X., to serve as a check on the results ; then 
ignite and again weigh: loss=organic and volatile matter. 

Step II. Evaporate 2000 c.c. of the water to dryness in a large porcelain dish, 
and heat gently till fumes of NH; cease to be evolved. Moisten the residue 
with 10 c.c. of distilled water, and then add 200 c.c. of dilute alcohol 
‘92 sp. gr.; having gently detached it all from the dish, filter and wash with 
similarly diluted alcohol till practically nothing more dissolves. This 
procedure is useful because it separates the salts present A ee 


(2) The filtrate may contain all salts of K and Na, chlorides and 
nitrates of Ca and Mg, and the sulphate of Mg. 

(2) The insoluble residue may contain the sulphate and carbonate 
of Ca and the carbonate of Mg, together with any iron and 
silicious matter present. 


(1) Analysis of the filtrate. 

(a2) Evaporate till the spirit is driven off, cool, transfer to a 250 C.c. 
flask, and make up to the mark with distilled water. Divide 
into two portions of 100 c.c. and 150 C.c. respectively, marking 
them a and B. , 

(4) To a add NH,Cl, NH,HO, and (NH,),C2O,, to precipitate the 
Ca, and estimate as usual as CaCOs. Calculate to CaO, and 
then x 2‘s=CaO present as Cl or NO; in the original 2000 C.c. 
of water taken. 

(c) To filtrate and washings from (4), concentrated to 50 c.c. and 
cooled, add Na,HPO, to precipitate Mg, treat as usual, and 
weigh as Mg,P,O,. Calculate to MgO, dnd then x 2°5=MgO 
present as Cl, SO4, or NOs in the original 2000 c.c. of water. 

(Z2) To B acidulate with HCl and add BaCl, to precipitate sulphate. 
Treat as usual and weigh as BaSOx. Calculate to SO3, and then 
x 2's + 1's = total SO; present in the original 2000 c.c. of 
water taken in combination with K or Na. 


‘150 QUANTITATIVE ANALYSIS OF METALS. 


(e) The filtrate and washings from (d@) are evaporated to a low bulk 
rendered alkaline with pure Ca(HO),, the separation for alkalies 
given at page 143 gone through, and the K and Na present 
both estimated as chlorides. Results x 2°5 + 1°5 = total K 
and Na present in the 2000 c.c. of water started with. 

(7) The residue from (e) is dissolved in a little water, and the K 
estimated thereon by PtCl, in the usual manner and calculated 
to K,O (see page 142). An equivalent amount of KCl. (calcu- 
lated from this KO) is then deducted from residue (e), and the 
balance is NaCl, which is calculated to Na,O. 


_ (2) Analysts of the insoluble portion. 


(a) This is washed from the filter with distilled water and then boiled 
with roo c.c. of H,O and HCl added till effervescence ceases. 
Any insoluble is filtered out, washed with boiling H,O, dried, 
ignited, and weighed = sz/icious matter in the 2000 c.c. of water 
started with. : 

(2) The filtrate and washings are warmed with a drop or two of 
HNO, and mixed with NH,C1+ _NH,HO, and the iron estimated 
if present as Fe,O,, and result calculated to Fe = total Fe in the 
2000 c.c. of water taken. 

(¢) Divide filtrate and washings into two equal parts, a and p. 

(Zz) The portion a is precipitated with (NH,),C,O,, and the calcium 
estimated as CaCO3 and calculated to CaO=total CaO as 
carbonate or sulphate in the original 2000 c.c. of water taken. 

(¢) The filtrate from (@) is concentrated to a low bulk, cooled, and 
Na, HPO, added with excess of NH,HO, and the Mg estimated 
as usual as Mg2P,O, and calculated to MgO. Result x 2=total 
MgO present as carbonate in the original 2000 c.c. of water. 

(f) The portion B is acidulated with HCl, and the sulphate estimated 
by BaCl,, weighed as BaSO, and calculated to SO;. Result 
x 2=total SO3 in combination with Ca in the original 2000 
c.c. of water. 


Step III. Evaporate 250 c.c. of the water to a bulk of 2 c.c., and treat in the 
nitrometer to estimate the nitric acid (see page 126). Resulting NO calcu- 
lated to N,O; and x 8 = total NO; present in 2000 c.c. of water. 


Step IV. Take the amount of chlorides volumetrically (page 115) in 100 c.c. 
of the water. Result x 20 = Clin 2000 c.c. of water. 


Step V. Calculation of results. 


(a) All our results being in grammes or fractions of the same from 
2000 C.c. of water, each must be multiplied by 35, which will bring 
them all to grains per imperial gallon (parts in 70,000), or 
multiplying the grammes per litre by 58°329 will bring them to 
grains per U.S. gallon. Now we state out our analysis thus 
(example taken from actual practice) :— 

A sample of water yielding 20°1 grains of total solids per gallon, of which *45 grain was 


‘* organic and volatile matter,” and the balance (19°65 grains) was mineral matter, showed on 
analysis :— 


(a) In the portion soluble in spirit : grains per gallon 
Potassium oxide : ; ; : : : "2704 
Sodium oxide . ‘ : é 4 ‘ ‘ 1°4097 
Chlorine . : : : “ : : 1°2133 
Sulphuric anhydride : ; ; : ; "6803 
Calcium oxide . : : . : : none. 
Magnesium oxide. 5 4 ; é : none. 


Nitric anhydride . . : é / j : none. 


QUANTITATIVE SEPARATIONS. 151 


a 


(4) In the portion insoluble in spirit : grains pex gallon. 
Calcium oxide . é - , ; : : 7°3953 
Magnesium oxide. ; : : F : I‘0000 
Sulphuric anhydride : : ; : ‘ 1°7647 
Silicious matter : : : : F roe ee 20K 
Ferric oxide. : : : - : ; "0500 





Total found 13°9837 


From this residue is now to be always deducted an amount of oxygen equivalent to the 
chlorine found, because all the bases have been calculated to oxides, while haloid salts con- 
tain no oxygen. The chlorine found is 1'2133, and— 


1°2133 X16 
yf 
Performing the deduction, we have: 
13°9837 — °2737 = 13°7100 grains of solid matter actually found. 


The total residue, after driving off organic matter, was 19°65 grains per gallon, and the 
difference is due to CO, unestimated, thus :— 
19°65 — 13°71 = 5°94 grains of CO, per gallon. 
Adding now this CO, to the substances actually estimated, we get: 
Total substances found + CO, = 19°65, 
Actual residue found = 19°65, 
which proves our analysis to be correct. 

It now remains to calculate how these bases and acids are probably combined as salts 
actually present, by the following general rules of affinity, thus :— 

(a) In the portion soluble in spirit. (1) Any sulphuric anhydride will prefer the bases in 
the following order: K, Na, Ca, Mg. (2) Chlorine will prefer the bases in the same order 
after the SO, is satisfied. Therefore we first calculate our K,O to K,SO,, which gives ‘50 and 
uses up ‘2296 of our SO, and the balance of SO, (‘4507) we calculate to Na,SO,. This gives 
‘80 Na,SO,, and leaves 1:0604 Na,O not as sulphate and therefore existing as chloride. Calcu- 
lating accordingly, we get 2°00 of NaCl, which just uses up all our chlorine. Therefore this 
portion contained altogether :-— 

Potassium sulphate : : : , , 50 
Sodium sulphate . : - ; ; : ‘80 
Sodium chloride 2°00 


(b) In the portion insoluble in spirit. (1) The SO, found will all be present as CaSO,, and 
the balance of CaO and all the MgO will be as carbonates. Therefore 1°7647 SO, calculated 
to CaSO, becomes 3'00 and uses up 1°2353 of CaO, leaving 6°16 to be calculated to CaCO. 
This yields 11°00 CaCO, and the 1°00 of MgO found calculated to MgCOs3 gives 2°Io. Thus 
this portion contains : 


= ‘2737 oxygen, equivalent to Cl found. 


Calcium sulphate . : : : é : 3°00 
Calcium carbonate ‘ : : : ee LOO 
Magnesium carbonate . , ; . : 2°10 
Putting now the whole analysis together, we have : 
Potassium sulphate. : ‘ : ‘50 
Sodium sulphate . : : ‘ : ; ‘80 
Sodium chloride . : ‘ ; 2°00 
Calcium sulphate . : ; : : : 3,00 
Calcium carbonate : : , : Ae € ro. 0) 
Magnesium carbonate . : : i . 2°10 
Ferric oxide. : ‘ - ; , ; 05 
Silica . ; ; : : : ‘ : ‘20 
Organic and volatile matter . : ; ‘ 45 


—— —_ 


Total residue 20°10. 


CHAPTER IX. 
ULTIMATE ORGANIC ANALYSIS. 


THIS process consists in estimating the amount of each element present in 
any organic compound, as distinguished from proximate analysis, which 
estimates the amounts of the compounds themselves. 


I, LIST OF APPARATUS REQUIRED. 


1. A combustion furnace, which is a series of Bunsen burners arranged 
in a frame so as to gradually raise a tube placed over them to a 
red heat. The tube lies ina bed made of a series of fire-bricks, 
which confine the heat and make it play all round the tube (see 
fig. 37). | 

2. Combustion tubes made of hard glass, not softening at a red heat. 
These tubes are closed at one end by drawing out before the 


" — 

fii ; SP 

\ ) —————$—$$——$———————— 

Al! ( 

— SS . 

@ = = eal 
U_——————— 








a ed ee Soe eee ey aes es || 














Fig. 38. Fig. 40. 


blowpipe and turning up. The mode of doing this is illustrated 
in fig. 38. 

3. U tubes packed with perfectly dry calcium chloride in small 
fragments, so as to allow the free passage of gases (illustrated 
ns. 39), and hereafter referred to for brevity as “CaCl, 
tubes.” 

4. Bulbs charged with strong solution of potassium hydrate (1 in 1), 
hereafter for brevity referred to as “‘KHO bulbs.” Two 
common forms of such bulbs are illustrated in fig. 4o. 


— 


ESTIMATION OF CARBON AND HYDROGEN. 153 





5. Bulbs for absorbing ammonia and intended to be charged with 
dilute acid of known strength, and hereafter referred to as 
‘nitrogen bulbs” for brevity. Two common forms of such 
bulbs are illustrated in fig. 41. 

6. Graduated tubes closed at one end to hold 50 c.c., and graduated 
from the closed end downwards in jyths of a c.c., used for 
collecting gases and measuring them after collection, hereafter 
referred to as “ gas collecting tubes ” for brevity (fig. 42). 

7. A deep cylindrical vessel of glass filled with water and furnished 
with a thermometer dipping in the water; the whole 
sufficiently high to permit of the entire immersion of the gas 
measuring tubes, and wide enough at the top to admit the 
hand, as shown in fig. 43. This is hereafter called the 
“measuring trough ” for brevity. 

8. Glass. towers, filled in one limb with fragments of CaCl, to absorb 
moisture, and in the other with fragments of soda lime to 





SSS == 


ii 
17 
N72 
Ni 












































Fig. 42. Fig, 43. 





absorb carbon dioxide. These are illustrated in fig. 44, and are 
used for freeing any air which may be caused to pass through 
them from moisture and CO,; hereafter called “‘air purifying 
towers ” for brevity. 


II. ESTIMATION OF CARBON AND HYDROGEN. 


This process is performed by heating a weighed quantity of the substance in 
a tube with some body readily parting with oxygen at a red heat, such as 
cupric oxide or plumbic chromate, by which the hydrogen and carbon of the 
organic body are respectively oxidised into water and carbonic anhydride. 
These products are passed first through a previously weighed tube containing 
calcium chloride, which retains the water, and then through a bulb apparatus 
containing potassium hydrate, which absorbs the carbonic anhydride and has 
also been previously weighed. After the experiment is finished, the increase 
in weight of the tubes is calculated thus :— 
As H,O: H,: : increase in CaCl, tube: ~. 
As CO,: C:: increase in KHO bulbs : x. 


The details of the actual process are as follows :— . 
Cupric oxide is prepared by heating cupric nitrate to bright redness in a 


154 ULTIMATE ORGANIC ANALYSIS. 





crucible ; it is reduced to powder while still warm, and preserved in a well- 
stoppered bottle. A combustion tube is procured, having a bore of about 
half an inch and a length of fifteen to eighteen inches. Sufficient cupric 
oxide to fill it is measured out, heated in a hard glass flask to expel any 
moisture (as it is very hygroscopic), well corked, and allowed to cool. About 
4 decigrammes of gently fused and cooled potassium chlorate is first dropped 
into the combustion tube, and then when cold a little oxide is introduced. 
About *4 gramme of the organic substance having been weighed out, it is rubbed 
up in a warm mortar with enough cupric oxide to half fill the tube, and the mix- 
ture is quickly transferred to that apparatus ; sufficient cupric oxide to nearly 
fill the tube is then introduced, and lastly a loose plug of asbestos is inserted to 
keep all in place. To this charged tube is then attached by means of a good 
cork a previously weighed ‘‘CaCl, tube,” and to this is in turn fixed by an 
indiarubber joint a set of ‘‘KHO bulbs,” also previously weighed. ‘The tube 
is now placed in the furnace, the glass attachments supported outside of it by 
appropriate stands, and made perfectly air-tight. Heat is now applied to the 
front portion of the tube by lighting the first five or six burners, and when 
that part is quite red-hot the next burner is turned on. The heat is thus 
applied gradually, taking care that it is so regulated as to produce a regular 
slow passage of the evolved gases, so that the bubbles may be distinctly 
counted as they pass through the ““KHO bulbs.” When the whole tube is 
heated from end to end the potassium chlorate at the back gives off a little 
oxygen, which sweeps the last traces of moisture and carbonic anhydride into 
the bulbs, which are then detached, weighed, and the increase in weight of 
each noted. 






































Weight of sugar taken . : : : ne ‘475 gramme. 
Potash bulbs after combustion weighed . ; . 79°I13 grammes. 
- », before <p be ee «735352 <A 
Difference, due to CO, . : ; “731 ~ 
Calcium chloride tube after combustion weighed . 23°605 grammes. 
9 33 before 93 39 : 23°330 29 
Difference, due to H,O . , : 275 = 
(C)12X "731, (H,) 2 X °275 
TE (OOya4 oc Let carbon. ~ (H,0) 18 = 03056 hydrogen. 
Total sugar taken . : : : : , - °475 
Total Cand H found . ; : : , . 22996 
Difference, due to oxygen. . °24504 
Or, in percentage—Carbon . : i A . : % ALOS 
Hydrogen ; ‘ ; “ : ; 6°43 
Oxygen... a ; : ; . . ‘Srs9 
100°00 








When the organic matter is a liquid, it is introduced into a small drawn-out 
tube previously tared ; the end is hermetically sealed by the blowpipe and the 
whole again weighed, thus obtaining the weight of the liquid. A little oxide 
having been first put into the combustion tube, the sealed one is dropped in, 
its end broken by a wire, and the whole of the rest of the oxide poured in. 
The heat is applied till six or seven inches of CuO are bright red, and then 
the burner underneath the spot where the tube with the liquid lies is 
cautiously turned on, so as to volatilise the vapor and cause it to pass over - 
the red-hot cupric oxide and so suffer combustion. Fats and other bodies 
which cannot be mixed with the oxide are weighed in a small platinum boat, 
which is dropped in and treated like the tube of liquid already referred to. 


ESTIMATION OF NITROGEN. 155 


a nana 


Special Notes to the Foregoing Process. 


(a) Substances containing sulphur, phosphorus, arsenic, chlorine, or any 
halogen, are best mixed with fused and powdered plumbic chromate 
instead of cupric oxide, so as to avoid the formation of volatile cupric 
compounds. 


(6) When the substance also contains nitrogen, the front part of the 
combustion tube must be plugged with a roll of bright copper gauze 
about 4 inches long instead of the asbestos. This is to reduce any 
oxide of nitrogen, which if allowed to pass into the potash would be 
absorbed and count as carbon dioxide. The copper, however, takes 
the oxygen, and only leaves nitrogen, which passes unabsorbed. 


(c) Very refractory bodies should be burned in a current of air or of 
oxygen carefully deprived of any moisture or carbon dioxide by causing 
it to pass through “ purifying towers ” (see page 153) before entering 
the tube. 


III. ESTIMATION OF NITROGEN. 


The estimation of nitrogen in all compounds, not being nitrites or nitrates, 
is conducted as follows :— 


(a) The Method of Varrentrapp and Will. This depends for its success 
on the fact that when nitrogenous substances are strongly heated with sodium 
hydrate, they are decomposed, forming a carbonate and oxide with the oxygen 
from the hydroxyl, and liberating hydrogen, which then combines with the 
nitrogen to form ammonia. 

So as to prevent fusion of the glass tubes employed, solution of sodium 
hydrate is evaporated to dryness with calcium oxide, and the resulting mixture, 
know as soda-lime, is heated to redness and preserved for use. 

About ‘5 gramme of the perfectly dry nitrogenous substance is mixed 
in a warm wedgewood mortar, with sufficient soda-lime to fill about three- 
quarters of a combustion tube. The mortar is rinsed with a little more 
soda-lime, and the rinsings also put into the combustion tube. More soda-lime 
is then put into the tube, until it is filled to within two inches of its open end, 
and then an inch of asbestos in shreds packed loosely in front of all, so as to 
prevent the passage of fragments of lime along with the evolved gases. A 
set of “nitrogen bulbs,” containing a little tolerably strong hydrochloric acid, 
is adapted to the mouth of the combustion tube by means of a well-fitting 
cork, and the tube is placed in the combustion furnace, so that the bulbs and 
about an inch of the tube project outside. A few front burners having been 
lighted, and the free part of the tube having become red-hot, the heat is 
gradually applied until the whole of it has been heated to bright redness. 
When this point is attained, and bubbles of gas cease to pass through the acid 
in the bulbs, the end of the tube is broken off, and some air sucked through 
the apparatus by means of a small tube attached to the outer end of the bulbs. 
The contents of the bulbs are then transferred into a small basin, the bulbs 
washed out into it, first by means of a little alcohol, and afterwards repeatedly 
with distilled water. An excess of platinic chloride is then added, the whole 
evaporated to dryness in a water bath, and the precipitate, having been 
moistened with a little alcohol, is washed on to a weighed filter. The washing 
with alcohol is continued until it passes colorless, and the precipitate is dried 
at 212° and weighed. The weight of the filter having been deducted, the 
balance is PtCly(NH,Cl),, which is then calculated to Np. 


156 ULTIMATE ORGANIC ANALYSTS. 
— een tenon mnt res alee actor lb 


A more simple plan, adapted to the estimation of nitrogen in manures and 
other commercial products, may be thus followed out :— 

The ammonia is received into 20 c.c. of*semi-normal volumetric solution of 
oxalic or sulphuric acid, which is placed in the bulb apparatus. The ammonia 
which passes into the bulbs during the combustion neutralises a portion of 
this acid, and at the conclusion of the operation the amount of acid still 
remaining free is ascertained by means of a corresponding normal volumetric 
solution of sodium hydrate (see VOLUMETRIC ANALYSIS, p. I 14). The difference 
between the amount of acid originally placed in the bulbs and that remaining 
free, as thus ascertained, evidently corresponds to the amount of sulphuric acid 
neutralised by the ammonia produced during the combustion. The strength 
of the acid being known, a simple calculation enables us to ascertain the 
amount of the nitrogen evolved in the form of ammonia. 


(2) The Process of Dumas. This consists in measuring the amount of pure 
nitrogen evolved, and is suitable for certain organic bases and for compounds 
containing nitrosyl (NO) or nitryl (NO,), in which the soda-lime fails to con- 
vert all the nitrogen into ammonia. 

The combustion tube (which in this case is twenty-six to twenty-eight inches 
long) is packed (1) with six inches of dry sodium hydrogen carbonate ; (2) 
with a little pure cupric oxide; (3) with the weighed substance mixed with 
CuO ; (4) with more pure CuO; and lastly with a considerable length of pure 
spongy metallic copper ; and the whole is closed by a good cork, through which 
passes a bent delivery tube, dipping under the surface of mercury in a small 
pneumatic trough. Heat is first applied to the very end portion of the 
NaHCO, until sufficient CO, has been given off to entirely drive all the air 
out of the apparatus, which is ascertained by collecting a little of the gas 
passing off and seeing that it is entirely absorbed by solution of potassium 
hydrate. A graduated “gas collecting tube” is then filled, one-third with 
strong solution of KHO, and the remainder with mercury, and carefully 
inverted into the mercury trough so that no air is admitted, and placed over 
the mouth of the delivery tube. Combustion is now commenced at the front 
of the tube and gradually carried backwards as usual. The gases evolved are 
CO, and N, the former of which is absorbed by the KHO and the latter 
collects in the graduated jar. When the heat reaches the back of the tube 
the remainder of the NaHCO, is decomposed, and the carbonic anhydride 
given off chases any trace of nitrogen out of the tube. The collecting tube 
is then closed by a small cup containing mercury, and transferred to the 
‘measuring trough,” and entirely immersed therein. After leaving it until its 
contents have acquired the temperature of the water, it is raised so that the 
level of the water inside and outside the tube is equal, and the volume is read 
off. ‘The temperature and pressure being noted, the weight of the nitrogen is 
obtained by the species of calculation already described at page 125. 


(c) Kjeldahl’s Process.—This method is rapidly superseding combustion, 


being almost universally employed by agricultural and food chemists. It is as 
follows :— 


The substance, whether solid or liquid,—and, if solid, it need not even be 
powdered,—is weighed or measured into a special hard glass flask, in which 
the subsequent treatment is executed. In the case of substances containing 
about to per cent. of nitrogen, about o'r to o'2 grm. are sufficient; if less is 
present, up to r grm. may be taken. Ten c.c. of the strongest sulphuric acid 
(previously proved to be free from ammonia) are now introduced by means of a 
pipette, and the flask having been placed in an inclined position upon wire gauze 
over a gas flame, the contents are heated for one or two hours nearly up to 
the boiling point of the acid, which may be known from the occasional slight 


or lM a ILON OF CHLORINE, SULPHUR, ETC. 157 


/ 





bumping. When the action of the acid is completed, which usually results 
in a solution of the solid, the flame is removed, and a fine spray of finely 
powdered permanganate of potassium (contained in a tube closed with a fine 
wire gauze and inserted in the neck of the flask) is made to rain down into 
the flask until its contents assume a green color. [This step is only, however, 
necessary when the substance is specially difficult to oxidise, most ordinary 
bodies being sufficiently attacked by fuming sulphuric acid.] The flask is 
then cooled, the contents diluted with water, and excess of strong solution 
of sodium hydrate having been added, it is immediately connected with a 
well-cooled condenser, provided with a receiver containing a measured 
amount of standard volumetric acid. The whole is then boiled until all the 
ammonia has distilled over into the receiver, and, finally, the ammonia is 
estimated by titrating back the contents of the receiver with volumetric soda, 
as described above under the soda-lime process. The ammonia found is 
calculated to nitrogen. Any substance likely to give off nitrous fumes should 
be first mixed with twice its weight of sugar. Nitrates require dilution with 
three times their weight of benzoic acid. To prevent bumping we place 
some fragments of recently ignited pipe-clay in the flask before distilling. 


IV. ESTIMATION OF CHLORINE, 


Chlorine is estimated by combustion of the substance in a tube filled with 
pure calcium oxide, when it displaces oxygen and turns part of the oxide into 
soluble calcium chloride. After combustion the contents of the tube are 
dissolved in diluted nitric acid, filtered, excess of argentic nitrate added, and 
the precipitate washed, dried, and weighed, as already directed (see Gravi- 
metric Estimation of Chlorine, p. 144). 


V. ESTIMATION OF SULPHUR AND PHOSPHORUS. 


Sulphur and phosphorus are estimated by fusing about 2 grms. of the solid 
substance in a silver crucible, with 24 grms. of pure potassium hydrate and 
3 grms. of pure potassium nitrate. After fusion the sulphur and phosphorus 
(which have been converted into sulphates and phosphates respectively) are 
estimated by dissolving the residue in water, slightly acidulating with hydro- 
chloric acid, and precipitating as barium sulphate and magnesium ammonium 
phosphate respectively, with the usual precautions. (See Gravimetric Estima- 

tion of Sulphates and Phosphates.) 


CHARTER SX 


THE ANALYSIS OF WATER, AIR, AND FOOD. 


DIVISION I. THE SANITARY ANALYSIS OF WATER. 


In the following instructions, the lines laid down by the Water Committee 
of the Society of Public Analysts (of which the author was a member) have 
been followed. 


Note.—These have been altered partly to correspond with processes used by American 
analysts, the main alterations being on albuminoid ammonia and hardness. 


1. Collection of the Sample. 


This is to be taken in a clean stoppered ‘‘ Winchester quart” bottle, 
previously entirely filled with the water, and emptied before finally filling up 
and introducing the stopper. The sample should be kept dark, and analysed 
with as little delay as possible. 


2. Color. 


This is to be taken by looking at a column of water in a colorless glass 
tube 2 feet long, and held over white paper. The presence of a greenish- 
yellow color is an adverse indication. 


3. Odor. 


An 8-ounce wide-mouthed stoppered bottle, free from odor, is half filled 
with the water, warmed in the water bath to 100° Fahr., shaken, and then the 
stopper is removed and the odor instantly noted. Peaty waters, and those 
containing marked amounts of sewage, can frequently be thus detected by 
a practised nose. 


4, Suspended Solids. 


Pass a litre of the turbid water through a dried and weighed filter. Dry 
the filter, and deposit at 120° C. and weigh. The gain in weight of the filter 
is the weight of suspended matter in a litre of water. 


5. Total Solid Residue. 


Heat a platinum basin of about 130 c.c. capacity to redness, cool it under 
the desiccator, and weigh. Introduce 100 c.c of the water, and evaporate 
over a low gas flame until reduced to about 10 c.c.; then place it on the 
water bath till dry. Finally, heat it in the air bath at 220° Fahr. until it 
ceases to lose weight, cool under the desiccator, and weigh. Having deducted 


THE SANITARY ANALYSIS OF WATER. 159 


the tare of the basin, the difference in milligrammes x ro = total residue in 
parts per million, or the same X 7 -+ Io = grains per gallon. Example :— 





Weight dish + residue . ‘ . 89°336 
Tare of dish . : 2m. < . 89°300 
036 or 36 milligrammes ; 
36X 7 : 
then “> 9 = 25°2 grains per gallon. 


The residue should now be gradually heated to redness, and the presence 
of organic matter carefully looked for as indicated by charring; also the 
nature of the same, by whether the odor on burning is purely carbonaceous 
(like burning sugar) or nitrogenous (like burning hair). This latter is an 
especially unfavourable indication. Total solids should not exceed 40 parts 
per 100,000. 


6. Chlorine. 


Solutions required :— 


(a) 4°789 grammes pure crystallised argentic nitrate, dissolved in 1000 c.c. of dis- 
tilled water. Each c.c. of this solution=‘oo1 (ome mzlligramme) of chlorine. 

(6) 5 grammes potassium chromate dissolved in 100 c.c. distilled water, and a weak 
solution of argentic nitrate dropped in until a slight permanent red precipitate 
is produced, which is allowed to settle in the bottle. 


Process.—Put too c.c. of the water into a white basin, add a few drops of 
the chromate solution, and titrate with the silver solution from a burette, 
graduated in 54, of c.c., until a faint permanent change of color is produced, 
as already described (Chap. VII., p. 115). Note the number of c.c. used, 
multiply -by 10, and the result will be chlorine in milligrammes per litre (or 
parts per million), or multiply by 7 and divide by 10, which will give grains 
per gallon (or parts per 70,000). The water itself must be perfectly neutral ; 
if acid it must be first shaken with a little pure precipitated chalk. The 
presence of a large amount of chlorine with excessive albuminoid ammonia 
indicates that the organic impurity is of animal origin, and if it then contains 
more than 15 parts per 1,000,000 the water should be condemned. 


7. Nitrogen in Nitrates, 


(a) Crum Process.—This is the best process where a nitrometer is available. 
250 c.c. of the water must be evaporated to a small bulk, the chlorine pre- 
cipitated with saturated solution of argentic sulphate, filtered, and the filtrate 
concentrated in a basin to 2 c.c. A nitrometer is charged with mercury, and 
the three-way stopcock closed, both to measuring tube and waste pipe. The 
concentrated filtrate is poured into the cup at the top of the measuring tube, 
and the vessel which contained it rinsed with 1 c.c. of water, and the contents 
added. The stopcock is opened to the measuring tube, and, by lowering 
the pressure tube, the liquid is sucked out of the cup into the tube. The 
basin is again rinsed with 5 c.c. of pure strong sulphuric acid, and this is also 
transferred to the cup and sucked into the measuring tube. The stopcock 
is once more closed, and 12 c.c. more sulphuric acid put into the cup, and 
the stopcock opened to the measuring tube until 10 c.c. of acid have passed 
in. The excess of acid is discharged, and the cup and waste pipe rinsed with 
water. Any gas which has collected in the measuring tube is expelled by 
opening the stopcock and raising the pressure tube, taking care no liquid 
escapes. The stopcock is closed, the measuring tube taken from its clamp 
and shaken by bringing it slowly to a nearly horizontal position and then 
suddenly raising it to a vertical one. This shaking is continued until no more 


160 THE ANALYSIS OF WATER, AIR, AND FOOD. 





gas is given off, the operation being, as a rule, quite complete in fifteen 
minutes. Now prepare a mixture of one part of water with five parts of 
sulphuric acid, and let it stand to cool. After an hour, pour enough of this 
mixture into the pressure tube to equal the length of the column of acidu- 
lated water in the working tube, bring the two tubes side by side, raise or 
lower the pressure tube until the mercury is at the same level in both tubes, 
and read off the volume of the nitric oxide. This volume expressed in c.c.’s 
and corrected to normal temperature and pressure gives, when multiplied by 
‘175, the nitrogen in nitrates, in grains per gallon, if 250 c.c. of the water 
have been used. According to some authorities the precipitation of the 
chlorides is not necessary. 

(6) Copper-Zinc Process—This must be carried out as follows:—A wet 
copper-zinc couple is prepared by taking a piece of clean zinc foil, about 
3 in. by 2 in., and immersing it in a solution of copper sulphate, containing 
about 3 per cent. of the pure crystallised salt. A copious and firmly adherent 
coating of black copper is speedily deposited upon the surface of the zinc, 
which must be allowed to remain in the solution until the deposit is thick 
enough, but not for too long a time, or it will become pulverulent and not 
adhere firmly to the zinc,—three or four minutes will generally be sufficient. 

The zinc coated with copper must then be removed from the solution, 
which may be bottled for subsequent use, and the couple thoroughly washed 
first with distilled water, and finally with the water to be analysed, in order 
that this may replace the adhering distilled water. It is then put into a clean 
6 or 8-ounce wide-mouth stoppered glass bottle, and covered with 100 c.c. of 
the water to be analysed. If the water be very soft a small addition, say one 
part per 1000, of sodium chloride will accelerate the reaction. The stopper 
must then be inserted in the bottle and the water allowed to remain overnight 
in a warm place. If still greater speed be necessary the temperature may be 
raised to 90° or 100° F, (32° or 38° C.). With hard water it is preferable to 
add a small quantity of pure oxalic acid to precipitate the lime and quicken 
the reaction. When the reduction is complete the fluid contents of the bottle 
are to be transferred to a retort with 200 c.c. of ammonia-free distilled water, 
and the retort having been attached to a condenser, the contents are distilled 
till the distillate which comes over gives no color with ‘“Nessler.” The 
distillate is then “‘ Nesslerised,” as already described (Chapter VII., page 128), 
and the number of milligrammes of NH; found are calculated to N (x 14 + 17), 
and then the resulting milligrammes of N x 7 -+ 10 = grains per gallon, 
or X 10 only = parts per million. 


8. Nitrites. 


Solutions required :— 


1. Dilute sulphuric acid (1°3). 

2. 5 grammes of metaphenylenediamine, and sufficient sulphuric acid to form an acid 
reaction dissolved in 1000 c.c. of water. ; 

3. 0406 grammes of pure dry silver nitrite dissolved in hot water, adding pure 
sodium chloride so long asa precipitate is formed, diluting to 1000 c.c. with 
water, and setting aside to deposit its silver chloride. 100 c.c. of the clear liquid 
are then diluted to1 litre. 1 c.c. of this solution contains ‘or mg. N,O3. 


Process—Put 100 c.c. of the water in a glass cylinder, and add 1 c.c. each 
of solutions 1 and 2. Prepare three other cylinders by diluting 5 c.c., 1 c.c., 
and 2 c.c. respectively to 100 c.c. with pure water, and adding 1 c.c. each of 
solutions 1 and 2. Compare the shade of the water cylinder with that of the 
others as described under “ Nesslerising.” The amount of N,O3 in the water is 
equal to that of the comparison cylinder having the same shade. 


THE SANITARY ANALYSIS OF WATER. 161 


9. Ammonia and Albuminoid Ammonia. 


These two indications are successively taken on the same quantity of water. 
The former is an estimation of the ammonia present in the water in the form 
of ammonium salts or similar compounds readily decomposed by a weak 
alkali, while the latter shows the ammonia derived from the decomposition of 
nitrogenous organic matter under the joint influence of an oxidising agent 
(KMnO,) and a hydrating agent (K HO), and is therefore a measure of the 
nitrogenous, and consequently presumably dangerous, organic matters con- 
tained in the water under examination. 

The solutions and apparatus required are :— 


(a) Sodium carbonate. 
_ A 20 per cent. solution of recently ignited pure sodium carbonate. 


(2) Alkaline potassium permanganate solution. 
Dissolve 200 parts of potassium hydrate and 8 parts of pure potassium per- 
manganate in 1200 parts of distilled water, and boil the solution rapidly till 
concentrated to 1000 parts, cool, and keep in a well-stoppered bottle. 


(c) Distilled water which zs free from Ammonia. 

Distilled water which gives no reaction with Nessler test is pure enough. But, if 
this is not available, take the purest distilled water procurable, add pure ignited 
sodium carbonate in the proportion of 1 part per 1000, and boil briskly until 
at least one-fourth has been evaporated. 


(d) A 40-ounce stoppered retort with a neck small enough to pass loosely into the 
internal tube of a Liebig’s condenser to the extent of 6 inches (see illustration, 
Chapter I., page 4). The joint between the retort and condenser is made by 
an ordinary indiarubber ring—such as those used for the tops of umbrellas— 
which has been previously soaked in a dilute solution of soda or potash ; being 
stretched over the retort tube in such a position that when the retort tube is 
inserted in the condenser it shall fit fairly tightly within the mouth of the tube 
about half an inch from the end. 


(e) Allthe materials for ‘‘ Nesslerising ” (see Chapter VII., page 128). 


The process is as follows :— 


(a) For free ammonia.—First test a little of the water with tincture of 
cochineal, to see if it shows an alkaline reaction. Put 500 c.c. of distilled 
water into the retort, and distil until 50 c.c. of the distillate gives no color 
with 12 c.c. of Nessler, thus rendering the whole apparatus “ammonia-free.” 
Let the whole cool, pour out the distilled water (which may be saved for 
ammonia-free water), put in 500 c.c. of the water to be analysed, and if it had 
not an alkaline reaction make it alkaline with a drop or two of the sodium car- 
bonate solution. The distillation should then be commenced. ‘The receiver 
should fit closely, but not air-tight, on to the condenser. The distillation 
should be conducted as rapidly as is compatible with a certainty that no spurt- 
ing takes place. The first 50 c.c. are collected in a cylindrical vessel, and the 
following 150 c.c. collected and thrown away, after which the fire is with- 
drawn. While these are passing over the first 50 c.c. are nesslerised, and the 
result plus one-third as much again is the amount of free ammonia in the 
500 c.c. 6f water. This multiplied by two gives milligrammes per litre or parts 
per million. 

(6) Lor albuminoid ammonia.—As soon as the distillation above referred to 
has been started, 50 c.c. of the alkaline potassium permanganate solution are 
placed in a flask with 150 c.c. of distilled water, and boiled gently during the 
whole time that the free ammonia is distilling, adding some ammonia-free 
water if necessary to prevent too much concentration. The object of this is to 
insure the entire evolution of any trace of ammonia present in the alkaline 
permanganate, thus avoiding a check analysis, as usually recommended. When 
the distillation of the free ammonia is complete, take out the stopper of the 
retort and pour in this boiled alkaline permanganate by means of a perfectly 

3 II 


162 THE ANALYSIS OF WATER, AIR, AND FOOD. 


a 


clean funnel with a long limb. Now replace the stopper and continue the 
distillation, when the albuminoid ammonia will begin to come over. The 
distillate is now collected in separate portions of 50 c.c. each, in glass cylinders, 
until three such portions have been collected. These are then separately 
nesslerised, when the sum of the ammonia found in each cylinder gives the 
albuminoid ammonia in soo c.c. of the water. This multiplied by two gives 
milligrammes per litre or parts per million. 

If a water yields no albuminoid ammonia it is organically pure ; but when 
the albuminoid ammonia reaches o‘r mg. per litre, the water is to be looked 
upon with suspicion, and is to be condemned if it reaches 0°15. When free 
ammonia is present in large quantity, a water yielding ‘o5 albuminoid ammonia 
is looked upon with suspicion (Wanklyn’s standards). Great care must be 
taken that no ammonia is kept in the room devoted to water analysis, and that 
all receivers used are first insured to be perfectly ammonia-free by proper 
rinsing with ammonia-free water and testing with Nessler. 


10. Oxygen required to oxidise the Organic Matter. 


Solutions required :— 


(a) Standard solution of Potassium permanganate. 

‘Dissolve ‘395 parts of pure potassium permanganate in 1000 of water. Each c.c. 

contains ‘OoOI gramme available oxygen. 
(4) Potassium Lodide solution. . 

One part of the pure salt recrystallised from alcohol, dissolved in 10 parts distilled 
water. ; 

(c) Dilute Sulphuric acid. 

One part by volume of pure sulphuric acid is mixed with three parts by volume of 
distilled water, and solution of potassium permanganate dropped in until the whole 
retains a very faint pink tint, after warming to 80° F. (26°6° C.) for four hours. 

(d) Sodium hyposulphite. . 
One part of crystallised sodium hyposulphite dissolved in 1000 parts of water. 
(e) Starch water. 

One part of starch to be intimately mixed with 500 parts of cold water, and the 

whole briskly boiled for five minutes, and filtered, or allowed to settle. 


The Process.—Two separate determinations have to be made: viz., the 
amount of oxygen absorbed during 15 minutes, and that absorbed during four 
hours ; both are to be made at a temperature of 80° F. (26 6° C.). It is most 
convenient to make these determinations in 120z. stoppered bottles, which 
have been rinsed with sulphuric acid and then with water. Put 250 c.c. of 
the water into each bottle, which must be stoppered and immersed in a water 
bath until the temperature rises to 80° F. (26°6° C.). _Now add to each bottle 
10 c.c. of the dilute sulphuric acid, and then 10 c.c. of the standard potassium 
permanganate solution. 

Fifteen minutes after the addition of the potassium permanganate, one of 
the bottles must be removed from the bath, and two or three drops of the 
solution of potassium iodide added to remove the pink color. After thorough 
admixture, run from a burette the standard solution of sodium hyposulphite, 
until the yellow color is nearly destroyed, then add a few drops of starch 
water, and continue the addition of the hyposulphite, until the blue color is 
just discharged. If the titration has been properly conducted, the addition of 
one drop of potassium permanganate solution will restore the blue color. 

At the end of four hours remove the other bottle, add potassium iodide, and 
titrate with sodium hyposulphite as just described. Should the pink color of 
the water in the bottle diminish rapidly during the four hours, further measured 
quantities of the standard solution of potassium permanganate must be added 
from time to time, so as to keep it markedly pink. 

The hyposulphite solution must be standardised, not only at first, but (since 


THE SANITARY ANALYSIS OF WATER. 163 


it is liable to change) from time to time in the following way :—To 250 c.c. of 
pure redistilled water add two or three drops of the solution of potassium 
iodide, and then 1o c.c. of the standard solution of potassium permanganate. 
Titrate with the hyposulphite solution as above described. ‘The quantity used 
will be the amount of hyposulphite solution corresponding to 10 c.c. of the 
standard potassium permanganate solution, and therefore representing 1 milli- 
gramme of oxygen consumed. The difference between the number of c.c. of 
hyposulphite used in the blank experiment and that used in the titration of 
the samples of water multiplied by the amount of available oxygen contained 
in the permanganate added (= 1 milligramme if 10 c.c. have been used), and 
the product divided by the number of c.c. of hyposulphite corresponding to 
the latter as found by the check experiment, is equal to the amount of oxygen 
absorbed by the water. 

Finally, the amount in milligrammes of oxygen absorbed thus found is 
multiplied by 4 for parts per million, and that result x 7 and + 100 = grains 
per gallon. 


11. Clark’s Process for Hardness. Total Jefore docling and permanent 
after boiling. Solutions, etc., required. . 
(a) Standard solution of Calcium chloride. 

Made by dissolving one gramme of pure calcium carbonate in the smallest excess of 
hydrochloric acid, then carefully neutralising with dilute ammonia, and 
making the solution up to a litre with distilled water. 

(6) Standard Soap solution. 


Dissolve 10 grammes of air-dried white Castile soap, cut into thin shavings, in a 
litre of dilute alcohol (sp. gr. 0'949). 

To determine whether this solution contains the proper amount of soap, 10 c.c. of 
the solution of CaCl, are diluted with 60 c.c. of water, and the soap solution 
added till a persistent lather forms on agitation. If 11 c.c.’of the soap solution 
have been used, it has the proper strength. If a greater or less quantity, it 
must be concentrated or diluted to proper strength. The soap solution, if 
turbid, must be shaken before using, but not filtered. 


The Process.—(a) or total hardness. Put 70 c.c. of the water into the 
bottle, of 250 c.c. capacity, and add the soap solution gradually from a burette. 
After each addition of soap solution, the bottle is shaken and allowed to lie 
upon its side five minutes. This is continued until, at the end of five 
minutes, a lather remains upon the surface of the liquid in the bottle. At 
this time the hardness is indicated by the number of c.c. of soap solution added, 
minus one. If magnesium salts are present in the water the character of the 
lather will be very much modified, and a kind of scum (simulating a lather) 
will be seen in the water before the reaction is completed. The character of 
this scum must be carefully watched, and the soap test added more carefully, 
with an increased amount of shaking between each addition. With this pre- 
caution it will be comparatively easy to distinguish the point when the false 
lather due to the magnesium salt ceases, and the true persistent lather is 
produced. If the water is of more than 16° of hardness, mix 35 c.c. of the 
sample with an equal volume of recently boiled distilled water, which has been 
cooled in a closed vessel, and make the determination on this mixture of the 
sample and distilled water. 

(6) For permanent hardness. To determine the hardness after boiling, boil 
a measured quantity of the water in a flask briskly for half an hour, adding 
distilled water from time to time to make up for loss by evaporation. It is 
not desirable to boil the water under a vertical condenser, as the dissolved 
carbonic acid is not so freely liberated. At the end of half an hour, allow the 
water to cool, the mouth of the flask being closed ; make the water up to its 
original volume with recently boiled distilled water, and, if possible, decant 


164 THE ANALYSIS OF WATER, AIR, AND FOOD. 
a eager ee 


the quantity necessary for testing. If this cannot be done quite clear, it must 
be filtered. Conduct the test in the same manner as described above. 

The hardness is to be returned in each case to the nearest half-degree. 
Good drinking water should not have a hardness of more than fifteen degrees. 


12. Judging the Results. 


No definite rule can be laid down for judging all the results on one uniform 
scale, because the analyst must have special information as to the locality, 
nature of the soil, or depth of the well, before giving a reliable opinion. For 
example, nitrates, which have in river and shallow surface waters the highest 
significance, as indicating the presence of previous sewage contamination, 
entirely lose such force in waters from deep artesian wells, because these are 
naturally rich in such salts. The same thing may be said of ammonia, which, 
although highly unfavourable in shallow waters, is yet always found in artesian 
wells, most probably from the metal pipes acting as reducing agents upon the 
nitrates. Again, with upland peaty waters we always find a large reduction of 
permanganate, and consequently an excess of “oxygen consumed,” although 
the organic matter so acting cannot be viewed as dangerous. 

Setting aside, however, all questions of mineral constituents, and only 
looking at the indications of the presence or absence of organic matter, the 
author has devised a valuation scale, originally presented by him in a paper 
read before the S.P.A., and which has proved since that time, in the hands 
of his various students dealing with sanitary examinations, as nearly correct 
as any general scale can be. The principle (which was originally proposed 
by the late Mr. Wigner) is to divide the amount of each figure found in the 
analysis by a fixed divisor, and where the quotient exceeds 10 to double all 
Figures over that number. Let us suppose that, for example, a water yielded 
‘o12 grain of albuminoid ammonia per gallon, and that the divisor fixed for 
this indication is ‘ooo7 ; then we have 


_OF? = 17'1; then 17°1 —10 = 71, and 7° X 2= 14'2; 
°0007 
therefore 14'2 + 10 = 24'2, indicated degree of impurity. 

To prevent the production of enormous figures, likely to startle non-pro- 
fessional persons, the indicated degree of impurity is expressed as a decimal 
by dividing it by 100. Thus, it is only when the article is very bad indeed 
that the indication comes into full numbers. 

Taking, then, the whole scale, it stands as follows :— 

GRAINS PER GALLON. 


Ammonia . A ‘ . : . each ‘oor15 = I. 
Albuminoid Ammonia . , ‘ : : >, ‘0007 = I. 
Oxygen consumed in 15 minutes. : ; » 004 =I. 
Oxygen consumed in 4 hours . . . op Ok cenete 
PARTS PER MILLION. 
Ammonia . ; : ; : : - each‘oz2 =I. 
Albuminoid Ammonia . : : ; : 5) CUE otek 
Oxygen in 15 minutes . : ; ° : » °057=1. 


Oxygen in 4 hours ; . . . » 143 =—1. 

When any number exceeds ro, then all over ro is to be doubled and added 
to the original number, and the total valuation is to be divided by too and 
noted as “comparative degree of organic impurity.” ‘Then, supposing no 
other consideration intervenes to modify the analyst’s opinion of the sample, the 
following limits should be observed :— 


Ist Class Water . - “ : : up to '25 degree (‘175 per million). 
2nd *;; », (more or less questionable) . «p70 ‘40 ,, aes ede 
Undrinkable Water . : : «OUP AO ae ae aa 25 


eS 


THE SANITARY ANALYSIS OF AIR. 165 


ee = 


DIVISION II. THE SANITARY ANALYSIS OF AIR. 


For sanitary purposes it is not necessary to make a full analysis of air, but 
should such be desired the processes described in Chapter XII. must be 
followed. The chief points are :— 


1. Estimation of Carbon Dioxide. 


This is done by the method of Pettenkofer, which consists in standardising 
r00 c.c. of lime or baryta water with standard oxalic acid 2°25 grammes per 
litre, of which 1 c.c. = ‘oor (1 milligramme of CaO). The air to be examined 
having been collected in a large bottle of known capacity, 100 c.c. of the 
same lime-water are added, the bottle is closed, and well shaken for some 
time. The CO, is absorbed, forming CaCOs. The resulting milky liquid is 
titrated in the bottle with the same acid. The indicator used is turmeric 
paper, or phenol-phthalein. The difference between the two titrations gives 
the amount of CaO precipitated as carbonate by the CO, in the air, and this 
is then calculated thus :— 


ee CO, present in the volume of air taken. 
In strict analyses, the volume of air taken must be corrected for observed 
temperature and pressure to its volume at N.T.P. Pure air contains about 
‘o4 per cent. of CO. 


2. Estimation of Organic Matter. 


A known volume of air is sucked by an aspirator through a specially 
arranged apparatus containing ammonia-free distilled water, and the resulting 
liquid is analysed for “free” and “ albuminoid ” ammonia like a water. 


3. Testing for Gaseous Impurities. 


The odor will generally detect these when present in notable proportions. 
Blotting-paper dipped (@) in tincture of turmeric, turns red-brown in presence 
of ammonia; (8) in solution of subacetate of lead—black with sulphuretted 
hydrogen ; (c) in solution potassium iodide mixed with starch paste—blue with 
chlorine or ozone; (d) weak solution of indigo is decolorised by chlorine and 
sulphurous acid gas; (e) red litmus paper dipped in solution of potassium 
iodide becomes blue with ozone and not with chlorine. 


DIVISION III. FOOD ANALYSIS. 


Here we will only attempt to consider a few of the more commonly occur- 
ring cases, always choosing the simplest and most rapid process. 


1, Milk. 


(1) Specific Gravity. Take the specific gravity with great care at 60° F. 
If not at 60°, take the temperature and refer to the table on p. 167. 

(2) Total Solids. Heat a small flat platinum dish about 13 inch in 
diameter to redness, cool it under the desiccator, and weigh. Put in about 
5 c.c. of the milk and again weigh. The difference = milk taken. Now dry 
on the water bath for 3 hours (or until seemingly dry), then transfer to the 
drying oven at 212° for 2 hours, cool under the desiccator, and weigh. Putit 
back in'the oven for an hour, repeat the cooling and weighing, and if the 
difference does not exceed a milligramme or two it is dry ; if it does, then 


166 THE ANALYSIS OF WATER, AIR, AND FOOD. 


repeat the drying. The weight of the dry residue mznus the tare of the dish 
equals the total solids; then— 
: weight solids x 100 
quantity taken 


(3) Fat. May now be calculated by Fleishmann’s formula thus (¢ = total 
solids: s = specific gravity: 7 = fat) :— 


100s — 100 
feat 033 a2 ee 


Deducting the fat thus found from the total solids, we get the ‘‘ solids not fat.” 





= per cent. of total solids. 


» 


If a more accurate process be required, the fat may be estimated by Adams’ 
method as modified by Thompson thus :— 

A strip of good filtering paper (not blotting) is procured, 21 in. long by 24 in. 
wide. Two small pieces of ordinary stirring rod are taken, the one rather longer 
than the other. These are fixed together by stretching a section of indiarubber 
tubing over each end of the rods. The two rods are separated from each 
other by the fingers, and the end of the strip of filter paper placed between 
them. The longer rod may be conveniently held by an iron clamp on a 
retort stand. . 5 c.c. of the milk are taken in a pipette, having a long stem 
under the bulb, and whilst the left hand holds the free end of the strip of 
paper, thus giving it an almost horizontal position, a small portion of the milk 
is allowed to run from the pipette, which is held in the right hand, with the 
finger closing the top, so as to make a line of milk across the strip of paper 
within about an inch of the fixed end. More milk is then allowed to flow on 
to the centre of the strip, and is then spread equally all over the surface with 
the stem of the pipette, which is held almost horizontally at right angles to 
the strip. By this means the milk may be transferred entirely to the 
strip of paper, about an inch or an inch and a half at the end being left 
unmoistened, upon which the stem of the pipette is wiped dry. ‘The strip of 
paper thus moistened with 5 c.c. of milk may now be taken between the 
hands, and dried in 2 or 3 minutes over an ordinary Bunsen burner. The 
flame may be allowed to play directly on the paper, which is moved rapidly 
backwards and forwards over it. The strip of paper thus treated is then 
coiled on a stirring rod, the rod withdrawn, and the coil without any further 
manipulation placed in a Soxhlet’s tube for extracting the fat (see Chapter IL., 
page 2). 

Be ol ae ie method of estimating fat is generally followed by most of the 
official milk analysts of America:—Replace the dish containing the total 
solids upon the water bath, and fill from a wash bottle with petroleum naphtha 
of the quality of benzine (U.S.P. 1880). Allow the benzine to boil down to 
about one-half and decant against a rod into a basin, replace upon the water 
bath, and again refill with naphtha and decant. Repeat this four times, then 
wash the outside of the capsule with benzine, dry the dish, and weigh as in 
total solids. ‘The loss of weight of the total solids is the fat in 5 c.c. of milk 
taken. 

(4) Added Water. The limit for the strength of milk is at present based 
upon that of the poorest possible natural milk. Average milk will show :— 

Fat “ . . 3°00 
Solids not fat 9°00 





Total 12°00 
If, however, a milk has only— 


Fat : : 3'0° 
Solids not fat ‘ : 8°5 


Total 1175; 


E07 


FOOD ANALYSIS—MILK. 






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168 THE ANALYSIS OF WATER, AIR,.- AND FOOD. 


it will not be considered as definitely proved to be adulterated. The amount of 
water added should, however, always be calculated upon the average standard o 
g per cent. ‘solids not fat,” provided the milk is certainly well below the limit 
of 8°5°/,. The “solids not fat” are used for the basis of calculation because 
they are a fairly constant quantity, the fat being variable. The amount of 
pure standard milk present in any sample may be calculated thus:— — 
solids not fat x 100 
9 


and the difference between this result and 100 is of course added water. 

(5) Ash. The total solids, or the residue from determination of fat, in the 
platinum dish are burned over a low flame at dull redness till quite white, and 
the ash is weighed. ‘The ash should be about *70°/., and it will never, as a 
rule, fall below °67 in an unwatered milk. 


= ¥ of pure milk present, 


2. Butter. 


Undoubtedly the best process for the detection of foreign fat in butter is :— 

Reichert’s Process.—This process is based upon the presence in butter-fat 
of one constituent (tributyrin), which yields by appropriate treatment an acid 
(butyric acid) that is relatively much more volatile than the other acids yielded 
by any of the practicable substitutes for butter-fat. As will be seen, the method 
is based on operations that admit of no arbitrary variation ; to secure reliable 
and comparable results exactly similar steps must be followed by all operators. 

2°5 grammes of the filtered melted fat are weighed into a flask of about 
150 C.c. Capacity, 20 c.c. of a solution of potassium hydrate in alcohol,— 
50 grammes K HO in 1000 c.c.,—and the whole heated to gentle ebullition on 
a water bath until the fat is entirely saponified and all the alcohol. expelled. 
The soap should form an almost dry mass, that can scarcely be detached from 
the bottom of the flask by shaking ; the last traces of alcohol being removed 
by occasionally sucking the air out of the flask with a tube. Afterwards 50 c.c. 
of water are added to dissolve the soap (the solution is hastened by gendle 
heating), and when the soap is completely dissolved, 20 c.c. of dilute sulphuric 
acid (100 c.c. H,SO,4 in 1000 c.c. of water) is added to decompose the soap. 
The flask is then connected with a small but efficient Liebig’s condenser, and 
the contents heated to moderate boiling, with addition of two or three bits 
of broken tobacco pipe to prevent bumping. The distillate, which contains 
some insoluble acids, must be passed, as it drops from the condenser, through 
a small wet filter into a 50 c.c. measure. The distillation is continued until 
exactly 50 c.c. has come over, which is at once titrated with decinormal soda 
solution, phenol-phthalein being used as the indicator, 

Reichert’s formula for determining the percentage of butter-fat in mixed fat 
is B=7°3 (7 — 0°3); ~ being the number of cubic centimetres of decinormal 
alkali used in neutralising the distillate from 2°s grammes of the fat. 

Thus treated, pure butter never yields less acidity than is represented by 
12 c.c. of decinormal soda (4 grammes veal NaHO perlitre). Butter made from 
the milk of one single individual cow has been known to fall to 11°5 c.c., but 
average butter, as produced from the mixed milk of a herd of cows, takes 
14 ¢.c, Every time a fresh lot of alcoholic potash (z in 20) is made, a blank 
experiment must be gone through without any fat, and the amount of alkali 
used must be noted on the potash bottle and deducted as a check from each 
actual analysis. ‘This is necessary when we employ methylated spirit, and such 
check may range up to 2 c.c. with certain spirit. 


Note.—Oleomargarine only requires ‘8 to ‘9 c.c. 3 cacao butter, 3°7 c.c.; lards “GO it.c. 
= NaHO to neutralise the volatile acids present. 


FOOD ANALYSIS. 169 


a nonce eee 


3. Bread. 


The only common impurity in bread detectable by chemical means is alum, 
which is tested for as follows:—A piece of the crumb of bread, cut from the 
centre of the loaf, is steeped in a mixture of 5 c.c. freshly made tincture of 
logwood, 5 c.c. of solution of ammonium carbonate, and 20 c.c. of water. The 
liquid is poured off and the basin placed on the top of the water oven. If 
alum be present a fine blue color will be developed. This test is, however, 
only very strong presumptive evidence ; and to absolutely confirm it in legal 
cases 100 grammes of the bread should be dried and incinerated in a large 
platinum basin, the ash dissolved in hydrochloric acid, and the amount of 
alumina present estimated by the ordinary methods of quantitative analysis. 
Proper precautions should be taken for separating silica and iron, and an 
allowance should be made on the alumina found from the amount of silica 
present, to avoid the estimation of Al,Os accidentally present as clay. The 
alumina is best precipitated and weighed as phosphate in the presence of 
ammonium acetate and excess of acetic acid, the solution being boiled and 
filtered hot. 


4. Estimation of the Alcoholic Strength of Spirits, Beer,’ Wines, and 
Tinctures. 


(1) Ina Pure Spirit. If the sample be simply a dilute spirit which leaves 
no residue upon evaporation, the percentage may be ascertained by taking 
the specific gravity. Great care must be taken that the contents of the 
specific gravity bottle are exactly at a temperature of 60° F., and in taking 
such specific gravities it is better to perform the operation, say, three times, 
and take the average of such determinations, as a very small error makes 
a great difference in the commercial value of the sample under examina- 
tion. Reference to the alcohol table appended will now give the required 
information. 


(2) In a Wine, Beer, Tincture, or Colored or Sweetened Spirit. The 
specific gravity of the sample is taken at 60° F.,(15°5°C.) and noted. roo c.c. 
are measured off at 60° F. (15°5° C.), and evaporated on the water bath or 
over 2 low gas flame, so as just to boil very gently, till all odor of alcohol 
has passed off. The liquid thus left is poured back into the measuring flask, 
the beaker is rinsed with a little distilled water, and the rinsings added to 
the flask. ‘The whole is cooled to 60° F., made up to the 100 c.c, mark with 
distilled water, and the specific gravity of this non-alcoholic fluid is then 
taken, also at 60° F. (15°5° C.). Lastly, we calculate :— - 


Gravity before boiling : : : ate 
—_>-_. _—___—= t fi ty of the contained spirit. 
Gravity after boiling Eas ere p38 P 


The gravity so found gives by the table the percentage of alcohol in the 
sample. 


y 


(3) Table for ascertaining the percentages respectively of Alcohol by 
Weight, by Volume, and as Proof Spirit, from the Specific Gravity. 


Condensed from the excellent Alcohol Tables of Mr. Hehner in the “Analyst,” vol. v., Dp. 43—63. 


Specific 
gravity, 
15‘5° 





I°0000 


"9999 
"9989 
9979 
9969 


Absolute | Absolute 


Alcohol 


by w’ght.|by vol’me 
Percent. | Percent. 





42°33 
42°81 
43°29 
43°76 
44°23 
44°68 


Alcohol 





Proof 
Spirit. 


Per cent. 





0°00 
OvI2 
1°28 
2°48 
3°85 
5°13 
6°34 
7°61 
8:90 
10°26 
11°62 
12°97 
14°50 
15°99 


17°43 


18°96 
20°50 
22°06 
23°70 
25°34 
26°99 
28°62 
30°26 
32°19 
33°96 
35°63 
37°30 
39°03 
40°64 
42°38 
44°12 
45°79 
47°39 
48°98 
50°57 
52°16 
ajo 3 
5518 
56°55 
57°94 
59°40 
60°66 
61°95 
63°30 
64°43 
65°55 
66:80 
68°04 
69°29 
70°40 
71°58 
72°50 
73°43 
74°39 
7537. 
79°45 
53 
78°61 
79°68 
80°75 
81°74 
82°69 
83°64 
84°58 
85°53 
86°47 
37°37 
88°26 
89°15 
90°03 
90°89 
91°73 








Specific 
gravity, 
15'5°. 


‘9189 
‘9179 
‘9169 
‘9159 
"9149 
"9139 
"9129 
‘9119 
‘9109 
"9099 
‘9089 
‘9079 
‘9069 
"9059 
"9049 
"9039 
"9029 
"9019 
"9009 
"8999 
"8989 
"8979 
"8969 


Absolute |Absolute 
Alcohol | Alcohol 


49°68 
50°13 
50°57 
51°00 
51°42 
51°83 
52°27 
52°73 
53°17 
53°61 
54°05 
54°52 
55°00 
55°45 
55°91 
56°36 
56°82 
57°25 
57°67 
58°09 
58°55 
59°00 
59°43 
59°87 
60°29 
60°71 
61°13 
61°54 
61°96 
62°41 
62°86 
63°30 
63°74 
64°17 
64°61 
65°04 
65°46 
65°88 
66°30 
66°74 
67°17 
67°58 
68°00 
68°42 
68°83 
69°25 
69°67 
70°08 
70°48 
70°88 
71°29 
vie 
72°13 
72°57 
73°00 
73°42 
73°83 
74°27 
74°73 


by w’ght.}by vol’me 
Per cent. 


Per cent. 


57°49 
57-97 
58°41 
58°85 
59°26 
59°68 
60°12 
60°56 
61°02 
61°45 
61°88 
62°36 
62°84 
63°28 
63°73 
64°18 
64°63 
65°05 
65°45 
65°85 
66:29 
66°74 
67°15 
67°57 
67°97 
68°36 
68°76 
69°15 
69°54 
69°96 
70°40 
70°81 
71°22 
71°62 
72°02 
72°42 
72°80 
73°19 
awry 
73°97 
74°37 
74°74 
75°12 


proot [specie | Weck | Absolute] peo 


Spirit, || Sravity, | by wght. |by vol’me| ,5Pirit. 
Per cent, 15'5% | Per cent. | Percent, | Per cent. 





92°56 || 8599 | 75°18 | 81-44 | 142°73 
93°39 || 8589 | 75°64) 81:84] 143-42 
94:22 || °8579 | 76°08 | 82°23 | 144°10 
95°05 || 8569 | 76°50 | 82°58 | 144°72 
95°88 || 8559 | 76°92 | 82°93 | 14534 
96°70 || 8549 | 77°33 | 83°28 | 145°96 
97°52 || ‘8539 | 77°75 | 83°64 | 146°57 
98°34. || 8529 | 78°16 | 83°98 | 147°17 
99°16 || 8519 | 78°56 | 84°31 | 147°75 
99°93 || 8509 | 78°96 | 84°64 | 148°32 

8499 | 79°36 | 84:97 | 14890 


‘9198 | 49°24 | 57°06 | 100-00Ps | -8489 | 79°76 | 85°29 | 149-44 


8479 | 80°17 | 85°63 | 150°06 
100°76 || *8469 | 80°58 | 85-97 | 150°67 
IOI'59 || 8459 | 81:00 | 86°32] 151'27 
102°35 || °8449 | 81°40 | 86°64 | 151°83 
10312 || ‘8439 | 81°80 | 86°96 | 152°40 
103°85 || 8429 | 82°19 | 87:27 | 152°95 
104°58 || 8419 | 82°58 | 87°58 | 153°48 
105°35 || ‘8409 | 82°96 | 87°88 | 154'01 
10615 || 8399 | 83°35 | 88°19 | 154°54 
106°93 || 8389 | 83°73 | 88-49 | 155°07 
107°69 || 8379 | 84:12 | 88°79 | 155°61 
10845 || 8369 | 84°52 | 8q:11 | 156°16 
109'28 || 8359 | 84:92 | 89°42} 156°71 
IlO'I2 |! 8349 | 85°31 | 89°72 | 157°24 
11092 || ‘8339 | 85°69 | 90°02 | 157°76 
III‘71_ || *8329 | 86°08 | 90°32 | 158°28 
112'49 || 8319 | 86°46 | 90°61 | 158°79 
113'26 || 8309 | 86°85 | go°90 | 159°31 
11399 || *8299 | 87:23 91°20] 159°82 
11469 || 8289 | 87°62 | 91°49 | 160°33 
II5‘41_ || ‘8279 | 88:00 | 91°78 | 160°84 
11618 || 8269 | 88:40 | 92°08 | 161°37 
11696 || 8259 | 88-80 | 92°39 | 161°91 
117°68 || 8249 | 89:19 | 92°68 | 162°43 
11841 _ || *8239 | 89°58 | 92°97 | 162°93 
IIQ'I2 || 8229 | 89°96 | 93°26 | 163°43 
11980 || 8219 | 90°32 | 63°52 | 163°88 
120°49 || 8209 | 90°68 | 93°77 | 16433 
12°18 || 8199 | 91:04 | 94°03 | 164°78 
121°86 || 8189 | 91°39 | 94'28 | 165°23 
122°61 || 8179 | 91°75 | 94°53 | 165°67 
123°36 || 8169 | 92°11 | 94°79 | 166712 
124°09 || ‘8159 | 92°48 | 95:06] 166758 
124°80 || 8149 | 92°85 | 95°32 | 167°04 
125°51 || 8139 | 93°22 | 95°58 | 167°50 
126'22 || 8129} 93°59 | 95°84 | 167°96 
126°92 || ‘8119 | 93°96 | 9611 | 168-24 
127°59 || 8109 | 94°31 | 96°34 | 168°34 
128'25 || 8099 | 94°66 | 96°57 | 169°24 
128'94 || 8089 | 9500 | 96°80 | 169°65 
129°64 || 8079 | 95°36 | 97°05 | 170°07 
130°33 || ‘8069 | 95°71 | 97°29 | 170°50 
130°98 || 8059 | 96°07 | 97°53 | 170°99 
131°64 || 8049 | 96-40 | 97°75 | 171°30 
13230 || 8039 | 96°73 | 97°96 | 171°68 
132°95 || 8029 | 97°07 | 98°18 | 172°05 
13360 || 8019 | 97°40 | 98-39 | 172°43 
134'25 || ‘8009 | 97°73 | 98-61 | 172°80 
134°90 || "7999 | 98°06 | 98°82 | 173°17 
135°51 || *7989 | 98°37 | 99°00 | 173°50 
136°13 || °7979 | 98°69 | 99°18 | 173'34 
136°76 || *7969 | 99°00 | 99°37 | 174°17 
137°49 || °7959 | 99°32 | 99°57 | 174°52 
138°05 || *7949 | 99°65 | 99°77 | 174°87 
138°72 || 7939 | 99°97 | 99°98 | 175°22 


139°39 
oe Absolute Alcohol. 
141°33 


142'03 || 7938 |r00:00 [10000 | 175'25 


FOOD ANALYSIS. 175 





5. Mustard. 


_ This is chiefly a microscopical matter for the exact identification of impuri- 
ties, but the following chemical operations may be performed :— 


(rt) Test a cooled decoction for starch with solution of iodine. 

(2) If starch be found, extract a weighed portion in the “Soxhlet” 
with petroleum spirit or ether. Distil off the spirit dry, and 
weigh the oil. Mustard contains as an ordinary minimum 
33% of oil, and the amount of genuine mustard in the sample 
will then be found thus :— 

% of oil found x 100 
33 
by deducting this from 100 the difference is added starch or 
flour. 

(3) Moisten the mustard with a little ammonia, when the turmeric brown 

will be developed if that coloring agent be present. 


= ¥% genuine mustard ; 


6. Pepper. 


This is also examined microscopically for extraneous starches (especially 
rice), and also for Aotvrette, which is chiefly ground olive stones. 


(1) Dry at 100° C., weigh out 5 grammes of the dried pepper, and take 
the ash. This should not exceed g’o per cent. even in the 
most inferior black pepper, which has been previously dried at 
too° C. Treat the ash with HCl, add water, boil, filter, wash, 
dry, ignite, and weigh the sand. This should not exceed 4 per 
cent. on the dried pepper. 


7. Coffee. 


If chicory be found by a microscopic examination of the sample—best done 
after boiling with dilute NaHO and washing—io grammes of the coffee are 
placed in a flask with 100 c.c. of distilled water. The flask is counter- 
balanced and the weights noted, and then it is boiled for a quarter of an 
hour. It is replaced on the scales, and the original weight restored by 
adding distilled water. Finally the decoction is filtered, cooled to 60° F. 
(15°5° C.), and its specific gravity is taken, The gravity of pure coffee extract 
obtained does not exceed 1009'5, while that of chicory solution is 1021°7. 
Supposing, therefore, that we obtained a gravity of 1015°5, then :— 

: 1021'7—1009'5 = 12°2, and 1015'5—1009'5 = 6°0; 
therefore— 

12'2: 6 2: 100 = 49 per cent. of chicory in the sample. 


8. Colored Sweets. 


The poisonous colors are nearly all mineral and insoluble. They may be 
scraped off, washed with water, and identified by the ordinary methods given 
in Chapter IV. As arule, at present only aniline colors are used, and they 
are added in such minute proportions as not to be considered dangerous. 


172 THE ANALYSIS OF WATER, AIR, AND FOOD. 





9. Direct Estimation of Starch in Cereals, and all Ordinary Articles 
of Food. 


This depends upon the fact that starch forms an insoluble compound with 
barium. If an excess of baryta water of known strength be added to starch 
which has been gelatinised in water, a portion of the barium will combine with 
the starch, and then by estimating the excess of baryta water left unabsorbed 
we can find the amount taken up by the starch. The formula of the starch- 
baryta compound is C,,H,4jO.)BaO, and it therefore contains 19°r per cent. 
of BaO. 


The materials required are :— 


(1) Decinormal hydrochloric acid, containing 3°65 grms. real HCl per 1000 c.c. ="00765 
BaO for each c.c. 


(2) Baryta water kept in a special jar with a burette permanently attached, as shown 
in the illustration below. A is the jar for the baryta water, having a tube 
attached containing lumps of quicklime to prevent the entrance of CO, from 
the air. The burette (B) is attached to the bottom neck of the jar by a tube 
having a pinchcock (@) to admit the reagent, and a tube (7) filled with lumps 
of caustic potash to prevent entrance of CQ,. 


(3) Alcoholic Solution of phenol-phthalein as an indicator. 


The Process—The sample is powdered or finely ground in a mill, and 

2 grammes weighed out for analysis. If it contains oil this is first extracted 
by percolation with petroleum 
spirit or ether in the “Soxhlet.” 
The powder is then well rubbed in 
with successive quantities of water 
until thoroughly disintegrated, the 
liquid being transferred to a 250 
c.c. flask, and 100 c.c. of water in 
all being used to entirely transfer 
the powder from the mortar to the 
flask. In dealing with very hard 
substances, like beans, peas, etc., 
the water should be used boiling. 
The flask and contents are now 
heated on the water bath for half 
an hour, with frequent shaking, 
to entirely gelatinise the starch. 
The whole is then cooled, and 
50 c.c. of standard baryta water 
having been added from the 
burette, the flask is corked, well 
shaken for two minutes, proof 
spirit is added up to the 250 c.c. 
mark, and the whole again shaken, 
tightly corked, and set aside to 
settle. While settling a check is 
made on ro c.c. of the baryta 
water mixed with 50 c.c. of freshly 
fiers: boiled distilled water, by titrating 

with the decinormal HCl, in the 

presence of two drops of phenol-phthalein. ‘The number of c.c. of acid used 





is recorded, giving the total strength of 10 c.c. of the baryta water employed. — 


When the main analysis has settled, 50 c.c. of the clear liquid are drawn off 


— 


| 


FOOD ANALYSIS. 173 





with a pipette, rapidly titrated with the decinormal acid and phenol-phthalein, 
and the number of c.c. of acid used is deducted from the check, and the 
difference in c.c. of acid is first multiplied by 5 and then by ‘0324, which 
gives the amount of starch in the 2 grammes taken for analysis. 


10. Free Sulphuric Acid in Vinegar. 


To a dilute solution of methyl violet add a drop of vinegar. A blue color 
shows the presence of a mineral acid in the sample. 

Mix 50 c.c. of the vinegar with 25 c.c. of volumetric solution of sodium 
hydrate, made decinormal by diluting the normal volumetric solution to ten 
times its bulk with water. The whole is evaporated to dryness, and 
incinerated at the lowest possible temperature. 25 c.c. of vigintinormal 
solution of oxalic acid (made to exactly balance the sodium hydrate solution) 
are now added to the ash, the liquid heated to expel CO,, and filtered. The 
filter is washed with hot water, and the washings having been added to the 
filtrate, phenol-phthalein solution is added, and the amount of free acid 
ascertained by running in decinormal soda from a burette. The number of 
c.c. of soda thus used multiplied by ‘oo49 gives the amount of free sulphuric 
acid in the vinegar. This process depends on the fact that whenever the ash 
of vinegar has an alkaline reaction, free mineral acid was undoubtedly absent. 


CHAPTER XI. 


ANALYSIS OF DRUGS, URINE, AND URINARY CALCULI 


DIVISION I. ANALYSIS OF DRUGS. 


1. General Scheme. 


THE analysis of drugs is so large a subject that only a few of the more 
commonly occurring problems can be discussed in the present volume. It 
will, however, be interesting, before proceeding to the consideration of special 
matters, to give a sketch of the general method of analysing a vegetable sub- 
stance used in medicine, following the lines laid down by Dragendorff, but 
somewhat modified by the author as the result of experience. 


Step I. 
Step II. 


Step III. 


Step IV. 


Step V. 


Step VI. 


Dry the substance in the water oven until it ceases to lose weight. 


Pack the dried and powdered substance, mixed with a little 
sand, in a “Soxhlet” apparatus, thoroughly exhaust it with 
petroleum spirit, and cork up and save the fluid extract so 
obtained, marking it A. 


Spread the solid left from Step II. out to dry on a plate of glass 
on the top of the water oven, and when all odor of petroleum 
has passed off, replace it in the Soxhlet, and exhaust it this time 
with perfectly anhydrous ether. Cork up the ethereal extract 
obtained and mark it B. 


Spread out as before, and when all odor of ether is gone, repack 
and extract with purified commercial methyl alcohol, as sold for 
making methylated spirit. This is more volatile than common 
alcohol, and is as a rule a better solvent of the articles required 
in this group, while it does not so readily extract glucose, etc. 
It is an article of commerce, and can be specially ordered 
through a purveyor of chemicals, as “ commercial methol, highest 
strength.”—Save this alcoholic extract and mark it c. 


Extract the insoluble matter from Step IV. with distilled water 
at a temperature not exceeding 49° C. (120° Fahr.), and filter. 
Wash with cold water and save the filtrate (D). 


Wash the insoluble off the filter into a large flask, with plenty 
of water, acidulated with 1 per cent. of hydrochloric acid, and 
boil it for an hour under an upright condenser. Let it settle, 
pour off the liquid as closely as possible (saving it), and then 
collect the insoluble on a filter and wash with boiling water, 
adding the washings to what was poured off. This extract is 
marked E. 


ANALYSIS OF DRUGS. 176 


rer a a te 


Step VIL. 


Step VIII. 


Once more wash the insoluble from the filter into a beaker, and 
boil it up for an hour with plenty of water rendered distinctly 
alkaline with sodium hydrate. Collect on a weighed filter, wash 
first with boiling water, acidulated with hydrochloric acid, and 
then with plain boiling water, till no trace of a chloride remains ; 
dry in the water oven and weigh, deducting the tare of the filter. 
Lastly, ignite the filter and its contents in a weighed platinum 
basin, and deduct the ash so found from the first weight, and the 
difference will be the woody fibre in the drug. 


Make a zztrogen determination by Kjeldahl’s method (page 156) 
on a fresh portion, and the nitrogen found (after deducting any 
due to alkaloids present) multiplied by 6°33 will give the amount 
of albuminous bodies present. 


Treatment of the Separate Solutions.—Each liquid is made toa definite 
number of c.c. with the same solvent, and then an aliquot part, say 
Io c.c., is taken and evaporated, and the residue weighed, to find the total 
matter soluble in each solvent. The bulk of the liquids are then treated as 


follows :— 


Liquid A. 


Liquid B. 


Liquid ©. 


Step I. 


This will contain chiefly fixed and volatile oils. The spirit is 
allowed to evaporate spontaneously, and the residue is distilled 
with water, when the volatile oil passes over, leaving the fixed 
oil in the retort. 


This chiefly contains resins, together with some bitters, alkaloids, 
and organic acids. The solution is evaporated to dryness on 
the water bath with sand, and the residue, having been powdered, 
is boiled with water slightly acidulated with HCl. A portion 
of this watery solution is tested for benzoic, cinnamic, salicylic, 
gallic, and other free organic acids, and the remainder is saved 
for subsequent use in Group C. ‘The portion insoluble in water 
now chiefly represents any resins present in the drug, which are 
soluble in ether. These may be further divided and examined 
by the action of alcohol. Resins are recognised by their odor 
on warming, and by the action of H,SO, HNO, HCl, etc., on 
spots of the solid resin left by evaporating the solutions. This 
matter requires special experience, but a full description of the 
nature and reaction of all the principal resins will be found in 
Muter’s ‘‘ Pharmaceutical and Medical Chemistry,” or in his book 
on ‘“ Organic Materia Medica.” | 


Is evaporated to a low bulk, and then poured into water faintly 
acidulated with hydrochloric acid. Any insoluble matter is 
probably a resinous body insoluble in ether, and is to be 
filtered out and examined as aresin. A portion of the aqueous 
solution is to be tested for tannin, and the remainder is to be 
mixed with the reserved liquid from B, the whole gently evaporated 
to a convenient bulk, and treated by immiscible solvents as 
follows :— 


The liquid (which must still retain a slightly acid reaction) is 
shaken up successively with chloroform and ether in a separator 
(see fig. 17, page 96). The solvents are drawn off and evaporated, 
and the residues so obtained tested for glucosides and bitter 


176 ANALYSIS OF DRUGS, ETC. 


a RA 


principles, of which latter bodies the following are some of the 
more commonly occurring :— 


(1) Extracted by chloroform from acid solutions :— 


Absinthin (wormwood). 

Anthemin (chamomiles). 

Colchicine (colchicum), imperfectly. 

Colocynthin (colocynth, or bitter apple), imperfectly. 

Calumbin, and probably some berberine (calumba), bright yellow, and 
highly fluorescent. 

Gentipicrin (gentian), very imperfectly. 

Picric acid (artificial), yellow, imperfectly. 

Picrotoxin (cocculus indicus), with difficulty. 

Quassiin (quassia wood). 


(2) Subsequently extracted by ether from acid solutions :— 


Chiratin (chiretta). 

Colocynthin (colocynth, or bitter apple). 
Gentipicrin (gentian). 

Picric acid, yellow. 

Picrotoxin (cocculus indicus). 


Note.—The alkaloid colchicine comes out with the glucoside in this division. 


Step II. The liquid remaining in the separator is now rendered alkaline 
with sodium hydrate and shaken up again with chloroform. 
This extracts nearly all the alkaloids). The chloroform is 
evaporated and the residue tested for alkaloids (see Chap. V.). 


Step III. The liquid still remaining in the separator is shaken up with 
amylic alcohol, which takes out morphine and leaves it on 
evaporation, when any residue is tested for its presence. 


Liquid D. Is evaporated to a low bulk and then mixed with twice its 
volume of rectified spirit, when gums precipitate insoluble, and 
may be examined, and sugars dissolve and may be estimated by 
“Fehling.” Saponin also may be found with the sugars. 


2, Assay of Cinchona Bark (AmERICAN METHOD). 


(A) For Total Alkaloids. 


Cinchona, in No. 80 powder, and fully dried at 100° C, (212° F.) 20 grammes, 
Lime . ; ; : 4 . A é ‘ 


: : : % 
Diluted sulphuric acid . ; a sufficient quantity. 
Solution of soda. ‘ , : : 3 : : : ; = ie 
Alcohol : . : ° : : : : . : 2 a - 
Distilled water . hae ; : ; : : ; - s 99 


Make the lime into a milk with 50 c.c. of distilled water, thoroughly mix 
therewith the cinchona, and dry the mixture completely at a temperature not 
above 80° C. (176° F.). Digest the dried mixture with 200 c.c. of alcohol, 
in a flask, near the temperature of boiling, for an hour. When cool, pour the 
mixture upon a filter of about six inches (15 centimetres) diameter. Rinse 
the flask and wash the filter with 200 c.c. of alcohol, used in several portions, 
letting the filter drain after use of each portion. ‘To the filtered liquid add 
enough diluted sulphuric acid to render the liquid acid to test-paper. Let 
any resulting precipitate (sulphate of calcium) subside; then decant the 
liquid, in portions, upon a very small filter, and wash the residue and filter 
with small portions of alcohol. Distil or evaporate the filtrate to expel all 


| ANALYSIS OF DRUGS. 177 


Sn ana 


the alcohol, cool, pass through a small filter, and wash the latter with 
distilled water slightly acidulated with diluted sulphuric acid, until the 
washings are no longer made turbid by solution of soda. To the filtered 
liquid, concentrated to the volume of about 50 c.c., when nearly cool, add 
enough solution of soda to render it strongly alkaline. Collect the precipitate 
on a wetted filter, let it drain, and wash it with small portions of distilled 
water (using as little as possible), until the washings give but a slight 
turbidity with test solution of chloride of barium. Drain the filter by laying 
it upon blotting or filter papers until it is nearly dry. 

Detach the precipitate carefully from the filter and transfer it to a weighed 
capsule, wash the filter with distilled water acidulated with diluted sul- 
phuric acid, make the filtrate alkaline by solution of soda, and, if a precipi- 
tate result, wash it on a very small filter, let it drain well, and transfer it to the 
capsule. Dry the contents of the latter at too° C. (212° F.) to a constant 
weight, cool it in a desiccator, and weigh. The number of grammes multiplied 
by 5 equals the percentage of total alkaloids in the cinchona. 


(B) For Quinine. 


To the total alkaloids from 20 grammes of cinchona, previously weighed, 
add distilled water acidulated with diluted sulphuric acid, until the 
mixture remains, for ten or fifteen minutes after digestion, just distinctly acid 
to test-paper. ‘Transfer to a weighed beaker, rinsing with distilled water, 
and adding of this enough to make the whole weigh 70 times the weight of 
the alkaloids. Add now, in drops, solution of soda previously well diluted 
with distilled water, until the mixture is exactly neutral to test-paper. 
Digest at 60° C. (140° F.) for five minutes, then cool to 15° C. (59° F.), and 
maintain at this temperature for half an hour. If crystals do not appear in 
the glass vessel, the total alkaloids do not contain quinine in quantity over 
8 per cent. of their weight (corresponding to 9 per cent. of sulphate of 
quinine, crystallised). If crystals appear in the mixture, pass the latter 
through a filter not larger than necessary, prepared by drying two filter 
papers of two to three and a half inches (5 to 9 centimetres) areas ae 
trimming them to an equal weight, folding them separately, and placing one 
within the other so as to make a plain filter, four-fold on each side. When 
the liquid has drained away, wash the filter and contents with distilled water 
of a temperature of 15° C. (59° F.), added in small portions, until the entire 
filtered liquid weighs go times the weight of the alkaloids taken. Dry the 
filter, without separating its folds, at 60° C. (140° F.), to a constant weight, 
cool, and weigh the inner filter and contents, taking the outer filter for a 
counter-weight. ‘To the weight of effloresced sulphate of quinine so obtained, 
add 11°5 per cent. of its amount (for water of crystallisation), and add o'12 
per cent. of the weight of the entire filtered liquid (for solubility of the 
crystals at 15° C., or 59° F.). The sum in grammes, multiplied by 5, equals 
the percentage of crystallised sulphate of quinine equivalent to the quinine in 
the cinchona. 

Cinchona should contain at least 3% total alkaloids ; yellow cinchona 27% 
quinine ; red cinchona 27 quinine. 


(C) British METHOD. 


Step I. Extraction. Mix 20 grammes of the bark in fine powder 
(No. 60) with 6 grammes of calcium hydrate in a mortar. 
Slightly moisten with 20 C.c. of water, and mix intimately ; 
allow the mixture to stand for an hour or two, when it will 


I2 


178 


a 


Step II. 


ANALYSIS OF DRUGS, ETC. 


present the characters of a moist, dark-brown powder, in which 
there should be no lumps or visible white particles. Transfer 
this powder to a suitable flask, add 130 c.c. of benzolated amylic 
alcohol B.P., boil them together for about half an hour under 
an upright condenser, decant, and drain off the liquid on to a 
filter, leaving the powder in the flask ; add more of the benzolated 
amylic alcohol to the powder, boil, and decant as before ; repeat 
this operation a third time ; then turn the contents of the flask 
on to the filter, and wash by percolation with more of the 
benzolated amylic alcohol until the bark is exhausted. In- 
troduce the collected filtrate, while still warm, into a stoppered 
glass separator ; add to it 2 c.c. of diluted hydrochloric acid, 
mixed with 12 c.c. of water; shake them well together, and 
when the acid liquid has separated draw it off, and repeat the 
process with distilled water slightly acidulated with hydrochloric 
acid, until the whole of the alkaloids have been removed 
(which is known by a few drops of the liquid ceasing to give 
any precipitate with sodium hydrate). The acid liquid thus 
obtained will contain all the alkaloids as hydrochlorates, and 
excess of hydrochloric acid. 


Separation of the Quinine and Cinchonidine from the 
Quinidine, Cinchonine, and Amorphous Alkaloids.—The acid 
fluid from Step I. is to be carefully and exactly neutralised 
with ammonia while warm, and then concentrated to the bulk 
of 18 c.c. 1's gramme of tartrated soda, dissolved in twice its 
weight of water, is added to the neutral liquid, and the mixture 
stirred with a glass rod. Insoluble tartrates of quinine and 
cinchonidine will separate completely in about an hour; and 
these collected on a filter, washed, and dried in the water oven, 
will contain eight-tenths of their weight of the alkaloids, quinine 
and cinchonidine, which multiplied by 5 represents the per- 
centage of those alkaloids. The other alkaloids will be left in 
the mother-liquor. | 7 


Step ILI. For total Alkaloids.—To the mother-liquor from the preceding 


Step IV. 


process add solution of ammonia in slight excess. Collect, 
wash, and dry the precipitate in the water oven, which will 
contain the other alkaloids. The weight of this precipitate 
multiplied by 5 gives the amount of cinchonine, quinidine, and 
amorphous alkaloids. This weight, added to that of the quinine 
and cinchonidine from Step II., gives the total alkaloids. 


Separation of Quinine and Cinchonidine.—This is an opera- 
tion to effect which with absolute accuracy requires special 
experience, and to give the detailed instructions and solubility 
allowances by which alone it can be carried out to within tenths 
of a per cent. would be beyond the scope of the present work. 
It may, however, be generally stated that it is accomplished 
by dissolving the precipitate from Step II. in a little water 
acidulated with hydrochloric acid, then adding excess of sodium 
hydrate, and shaking up with ether. After standing for some 
hours, the ethereal layer is separated and evaporated to dryness. 
The residual quinine (now containing only a little cinchonidine) 
is then treated as in the American instructions for quinine 


(B, page 177). 


ANALYSIS OF DRUGS. 179 





Step V. Separation of the quinidine, cinchonine, and amorphous alkaloid. 
The precipitate from Step III. is digested in cold proof spirit, 
which dissolves the quinidine and amorphous alkaloids, and 
leaves the cinchonine insoluble for collection, drying, and 
weighing. ‘The alcoholic solution is rendered acid with acetic 
acid, and evaporated to dryness on the water bath. The 
residue is dissolved in a very small quantity of water, and a 
little spirit and some solution of sodium iodide is added, which 
precipitates the quinidine as iodide. This is weighed, and the 
weight multiplied by *718 = quinidine. The amorphous alkaloids 
are then found by difference. | 


3. Assay of Opium. 


Opium, in any condition to be valued . ; : ‘ . 7 grammes. 

Lime, freshly slaked . : : ; - ‘ . Sse of 

Chloride of ammonium . : ‘ owe es 

Alcohol : ‘ s . ; ‘ : : : . asufficient quantity. 
Stronger ether ; ; : d ‘ 4 : ; ft a 
Distilled water . : ‘ : ; : ; : : ‘; ys 


Triturate together the opium, lime, and 20 c.c. of distilled water, in a 
mortar, until a uniform mixture results ; then add 50 c.c. of distilled water, 
and stir occasionally, during half an hour. Filter the mixture through a 
plaited filter, 3 to 34 inches (75 to go millimetres) in diameter, into a 
wide-mouthed bottle or stoppered flask (having the capacity of about 120 c.c. 
and marked at exactly 50 c.c.), until the filtrate reaches this mark. To the 
filtered liquid (representing 5 grammes of opium) add 5 c.c. of alcohol 
and 25 c.c. of stronger ether, and shake the mixture ; then add the chloride 
of ammonium, shake well and frequently during half an hour, and set it aside 
for twelve hours. Counterbalance two small filters, place one within the 
other in a small funnel, and decant the ethereal layer as completely as 
practicable upon the filter. Add ro c.c. of stronger ether to the contents 
of the bottle, and rotate it ; again decant the ethereal layer upon the filter, 
and afterwards wash the latter with 5 c.c. of stronger ether, added slowly and 
in portions. Now let the filter dry in the air, and pour upon it the liquid in 
the bottle, in portions, in such a way as to transfer the greater portion of the 
crystals to the filter. Wash the bottle, and transfer the remaining crystals to 
the filter, with several small portions of distilled water, using not much more 
than 10 cc. in all, and distributing the portions evenly upon the filter.* 
Allow the filter to drain, and dry it, first by pressing it between sheets of 
bibulous paper, and afterwards at a temperature between 55° and 60° C. (T3a17 
to 140° F.). Weigh the crystals in the inner filter, counterbalancing by the 
outer filter. The weight of the crystals in grammes, multiplied by 20, 
equals the percentage of morphine in the opium taken. 

Opium in its normal moist condition should yield not less than 9% of 
morphine. 

Powdered opium should yield not less than 12 nor more than 16% of 
morphine. 

Denarcotised opium should yield 14 °/, of morphine. 


4. Estimation of the Alkaloidal Strength of Extracts. 


Dissolve 1 gramme of the extract in twenty c.c. of water, heating gently if 


a RADAR ERMEEE TESLA.» 


* When it is desired to obtain the morphine in a state of absolute purity, the precipitate 
should be washed first with water saturated with morphia, and then with rectified spirit 
similarly saturated. 


180 ANALYSIS OF DRUGS, ETC. 


ee a ae ne Ne nse ee Seem ce 


necessary, and add 6 grammes of sodium carbonate previously dissolved in 
20 c.c. of water and 20 c.c. of chloroform ; agitate, warm gently, and separate 
the chloroform. Add to this 20 c.c. of dilute sulphuric acid with an equal 
bulk of water ; again agitate, warm, and separate the acid liquor from the 
chloroform. ‘To this acid liquor add now an excess of ammonia, and agitate 
with 20 c.c. of chloroform ; when the liquors have separated, transfer the 
chloroform to a weighed dish, and evaporate the chloroform over a water 
bath. Dry the residue for one hour at 1oo°® C. (212° F.), and weigh. Thus 
treated, extract of zux vomica should show 15 per cent. of total alkaloids, and 
the process may be extended to almost any extract containing alkaloids except 
opium. No standards have, however, yet been fixed. 


5, Examination of a Tincture or other Alcoholic Liquor for the Presence 
of Methylated Spirit. 


U.S.P. Method for Alcohol.—Digest 150 c.c. for an hour with 20 grains 
of carbonate of lead, and filter. Distil over a water bath till 20 c.c. have 
passed over. Add to the distillate 1 c.c. test solution of permanganate of 
potassium. ‘The color should not disappear within one or two minutes ; if 
discharged sooner than one minute methyl alcohol was present. 

For the purpose of testing tinctures or any alcoholic liquors, they must 
first be distilled until a part of the spirit has passed over. The distillate is 
treated as follows :— 


A small flask is fitted with a cork and a tube having two right-angular 
bends, with the end dipping into a test-tube kept cold by immersion in water ; 
and in it is put,— : 

(1) About half a drachm of the spirituous liquid required to be tested. 

(2) An equal quantity of potassium dichromate and of pure sulphuric acid. 

(3) Four or five times as much water. 


The mixture, after standing for twenty minutes, is distilled at a gentle heat, 
until nearly the whole has passed over. Sodium carbonate having been added 
to the distillate till it is slightly alkaline, the liquid is evaporated in a porce- 
lain basin to about half its bulk, and having been acidulated slightly by acetic 
acid, is transferred to a test-tube, heated gently with twenty drops of a 5 per 
cent. solution of argentic nitrate for a few minutes, when any decided opacity 
(due to the discoloration of the fluid, and the separation of a blackish precipi- 
tate of metallic silver) indicates the presence of methyl hydrate in the sample 
thus tested. In the oxidation of ordinary alcohol, a mere trace of formic acid 
is formed by secondary decomposition ; consequently a distinct precipitate 
must be obtained before the spirit can, with certainty, be pronounced to be 
methylated. 

The operation of the above process depends on the fact that by a short 
oxidation with sulphuric acid and potassium dichromate, aldehyds and acids 
are produced, which, by being boiled with sodium carbonate, yield sodium 
acetate and formate, the former from the ordinary “alcohol,” and the latter 
from the wood spirit. Upon the addition of argentic nitrate, argentic formate 
is produced, which is easily reduced by boiling to metallic silver, while argentic 
acetate is not so affected. If the oxidation be too powerful, the formic 
acid in turn becomes oxidised to CO, and H,O and lost. ‘Thus the 
process is not always satisfactory, and must be completed within half an hour 
or SO. 

When this process has to be applied to sweet spirit of nitre, the ethyl nitrite 
must be first got rid of, as follows :— 

Take a little of the spirit and place it in a bottle with some dry potassium 


ANALYSIS OF DRUGS. | 181 


a nee nEEE NEE NREEE EERE 


carbonate, and shake up. Let it settle, and take about two drachms of the 
strong spirit which separates. Saturate this with calcium chloride, and distil 
on a water bath, rejecting the distillate (ethyl nitrite, etc.). Add a little 
water to the contents of the retort and distil again, when the pure spirit will 
come over, and a portion may then be tested as above directed. 

Examination of official ethers :— 

When tro c.c. are agitated with an equal volume of glycerine in a graduated 
test-tube, the ether layer, when fully separated, should not measure less than 
7°5 c.c, for ether, 8°6 c.c. for stronger ether, or 9 C.c. for acetic ether. 


6. Estimation of the Strength of Resinous Drugs. 


Take 5 to 10 grammes of the drug in powder, and place it in a strong glass 
flask with 100 c.c. of pure alcohol (U.S.P. and free from resin). Close the 
flask with a good cork, and digest it in a warm place at about 49° C. (120° F.) 
for 12 hours, shaking from time to time. Pour or filter off 80 c.c. (representing 
38, of the total drug taken), place it in a weighed beaker, and evaporate to 
25 c.c. on the top of the water bath. Now add 50 c.c. of distilled water, and 
boil gently over a low gas flame till all the alcohol is driven off. Let it cool 
and perfectly settle, pour off the supernatant liquor, wash the deposited resin 
by decantation with hot distilled water, and then dry the beaker and its 
contents in the air bath at 105° C. (220° F.) and weigh, deducting the tare 
of the beaker. ‘Thus treated, jalap, for example, should show 12 per cent 
of resin, of which not over 1o per cent. should be soluble in ether. 
Scammony should show 75 per cent. resin, which is entirely soluble in ether, 
and in solution of potassa. From the latter it is not re-precipitated by dilute 
hydrochloric acid in excess. For other resinous drugs no official standard 
has yet been laid down. 


7. Testing the Purity of Quinine Sulphate (Official B.P. Directions). 


Test for Cinchonidine and Cinchonine.—Heat 100 grains of the sulphate of 
quinine in five or six ounces of boiling water, with three or four drops of 
diluted sulphuric acid. Set the solution aside until cold. Separate, by 
filtration, the purified sulphate of quinine which has crystallised out. To 
the filtrate, which should nearly fill a bottle or flask, add ether, shaking 
occasionally, until a distinct layer of ether remains undissolved. Add 
ammonia in very slight excess, and shake thoroughly, so that the quinine at 
first precipitated shall be redissolved. Set aside for some hours, or during 
a night. Remove the supernatant clear ethereal fluid, which should occupy 
the neck of the vessel, by a pipette. Wash the residual aqueous fluid and 
any separated crystals of alkaloid with a very little more ether, once or twice. 
Collect the separated alkaloid on a tared filter, wash it with a little ether, 
dry at 212° F. (100° C.), and weigh. our parts of such alkaloid correspond 
to five parts of crystallised sulphate of cinchonidine or of sulphate of cin- 
chonine. 

Test for Quinidine.—Recrystallise 50 erains of the original sulphate of 
quinine, as described in the previous paragraph. ‘To the filtrate add solution 
of iodide of potassium, and a little spirit of wine to prevent the precipitation 
of amorphous hydriodates. Collect any separated hydriodate of quinidine, 
wash with a little water, dry, and weigh. The weight represents about an 
equal weight of crystallised sulphate of quinidine. 

Test for Cupreine.—Shake the recrystallised sulphate of quinine, obtained 
in testing the original sulphate of quinine for cinchonidine and cinchonine, 
with one fluid ounce of ether and a quarter of an ounce of solution of 


182 ANALYSIS OF DRUGS, AIC. 


ammonia, and to this ethereal solution, separated, add the ethereal fluid and 
washings also obtained in testing the original sulphate for the two alkaloids 
just mentioned. Shake this ethereal liquor with a quarter, of a fluid ounce 
of a 10 per cent. solution of caustic soda, adding water if any solid matter 
separates. Remove the ethereal solution. Wash the aqueous solution with 
more ether, and remove the ethereal washings. Add diluted sulphuric acid 
to the aqueous fluid heated to boiling, until the soda is exactly neutralised. 
When cold collect any cupreine sulphate that has crystallised out on a tared 
filter, dry, and weigh. 


Quinine sulphate should not contain more than 5 per cent. of other cinchona 
alkaloids. 


8. Assay of the Alkaloidal Strength of Scale Preparations. 


Dissolve 4 grammes of the scales in 30 c.c. of water, in a capsule, with the 
aid of heat. Cool, and transfer the solution to a glass separator, rinsing the 
capsule ; add an aqueous solution of o'5 gramme of tartaric acid, and then 
solution of soda in decided excess. Extract the alkaloid by agitating the 
mixture with four successive portions of chloroform, each of 15 c.c. Separate 
the chloroformic layers, mix them, evaporate them in a weighed capsule, 
on a water bath, and dry the residue at a temperature of 100° C. (212° F.). 
Thus treated, citrate of iron and quinine should show 12 per cent. of alkaloidal 
residue, which should be soluble in ether. Solution of citrate of iron and 
quinine (operate on 8 grammes) should yield 6 per cent. of quinine ; citrate of 
iron and strychnine should yield 1 per cent. of strychnine. 


9. The Estimation of Phenol. 


The following is the method for determining the phenol quantitatively in 
crude carbolic acid :—2z0 c.c. of potassium hydrate solution (sp. gr. 1°25—1°30) 
are added to 20 c.c. of the crude carbolic acid. The whole is well shaken up, 
and, after half an hour, the mixture is made up to # litre by the addition 
of water. The tarry constituents of the carbolic acid separate out and are 
removed by filtration. The residue is washed with lukewarm water till the 
wash-water is no longer alkaline. The whole filtrate is then treated with 
hydrochloric acid till faintly acid (this point is also indicated by the liquid 
changing color and turning brown), and made up to 3 litres. The small 
quantity of tarry matter left in the filtrate does not interfere in the titration 
which follows. ‘The dilution is necessary, for, in titrating, the carbolic acid 
solution must not contain more than ‘1 gr. in 25 c.c. 

50 c.c. are now taken, and 150 c.c. of a solution containing 2’o40 grs. 
sodium bromate and 6’959 grs. sodium bromide to the litre are added, 


together with 5 c.c. of concentrated hydrochloric acid; bromine is evolved 
and tribromophenol precipitated. 


C,H;HO + 6Br = C,H,Br,HO iS SHEE. 


After 20 minutes, during which the mixture is shaken up frequently, ro c.c. 
potassium iodide solution (125 grs. potassium iodide to the litre) are added ; 
potassium bromide is formed with the excess of free bromine, and iodine 
liberated. After about 5 minutes (not longer) starch solution is added, and 
the free iodine titrated with a sodium thiosulphate solution (“hypo”), con- 
taining 9°763 grs. per litre. | 

The experiment should be first done upon ‘2 gramme of pure crystallised 
carbolic acid dissolved in 50 c.c. of water, and the number of c.c. of the 
‘hypo ” solution used should be noted. A blank experiment on 150 c.c. of 


es 


ANALYSIS OF DRUGS. 183 


ane aca c a aac a reac aca e ana ee citEnaEn nea 


the bromide-bromate solution, with 5 c.c. of HCl and 10 c.c. of the iodide 
solution, should also be titrated. By deducting the c.c. of “hypo” used in 
the first check from that in the second, the number of c.c. of “hypo” 
equivalent to ‘2 gramme real carbolic acid is ascertained, and the equivalent 
value of each c.c. of “hypo” in carbolic acid is calculated. In every analysis 
the number of c.c. of “hypo” used is dgducted from that employed in the 
blank experiment, and the difference is calculated to carbolic acid present 
in the sample. If 34 “hypo” is used, each c.c. will represent ‘601567 phenol. 

The amount of water contained in a solution of carbolic acid may be 
determined by agitating the solution, in a graduated cylinder, with an equal 
volume of chloroform. After standing, the upper layer consists of the water 
contained in the mixture.—U.S.P. 


10. Estimation of the Fatty Acids in Soap. 


Two grammes of the soap, in fine shavings, are shaken up in a separator, with 
a slight excess of dilute sulphuric acid to liberate the acids. Ether is then 
added, and the fatty acids which have been liberated are dissolved up in it. 
When the decomposition of the soap is complete, the liquid below the 
ethereal solution is removed. With a little care this can be done very 
completely without any loss of the ethereal solution. ‘The ether is then 
shaken up with distilled water, and the latter drawn off as before, and this 
process of washing repeated three times more. When all but a few drops of 
the wash-water have been drawn off, a few drops of barium chloride solution 
are added, the mixture shaken up, and the last traces of sulphuric acid thus 
removed. With a little practice so little water is left below the ethereal 
solution that the latter can be directly drawn off and evaporated in a weighed 
dish, and the residue finally dried in the water oven and weighed. ‘The fatty 
acids obtained are perfectly free from sulphuric and hydrochloric acids, and do 
not get brown at 100° C. 


11. Estimation of Oleic Acid. 


One gramme of the impure fatty acid is saponified in a basin by heating 
with a slight excess of alcoholic potash till dissolved, and then diluted with 
water. This solution is treated with acetic acid drop by drop, until on stirring 
a faint permanent turbidity ensues. Dilute solution of potassium hydrate is 
then stirred in drop by drop till the liquid just clears up, and then solution of 
plumbic acetate is stirred in until precipitation ceases. The precipitate having 
been allowed to settle, the supernatant liquor is poured off and the soap 
washed once with boiling water. A little clean sand is rubbed up with the 
soap in the basin, and the whole scraped out and transferred to a ‘‘ Soxhlet,” 
in which it is thoroughly exhausted with go c.c. of pure ether. The ethereal 
solution (which now contains only plumbic oleate, the plumbic palmitate and 
stearate being left insoluble in the Soxhlet) is transferred to a special apparatus, 
sold by apparatus vendors as “ Muter’s oleine tube.” ‘This isa graduated and 
stoppered tube holding 120 ¢.c., and having a spout and stopcock at 30 C.c. 
from its base. Previously to introducing the ether, place 20 c.c. of dilute 
hydrochloric acid (1 in 3) into the tube, and then make up the whole with 
ether rinsings of the basin to the 120 c.c. mark. Close the tube, shake well, 
and set aside. When settled, note the full volume of the ethereal solution 
of oleic acid, and run off an aliquot part from the tap into a weighed dish, 
evaporate, dry in the water oven, and weigh. Finally calculate this weight to 
that of the whole bulk of ethereal solution previously noted, thus getting the 
amount of real oleic acid present in the gramme of crude acid started with. 


184 ANALYSIS ‘OF URINE, “ETC. 


12. Estimation of Glycerine. 


This process depends on (1) obtaining the glycerine free from other oxi- 
disable bodies, such as alcohol sugars, etc. ; (2) oxidising it with potassium 
bichromate in the presence of sulphuric acid to carbon dioxide and water by the 


following equation :— r 


3C3H,(OH), + 7K,Cr,0, + 28H,SO,=7Cr.(SO,); + 7K,SO, + 9CO, + 40H;0 ; 


and (3) estimating the amount of CO, evolved. 

The relation between carbon dioxide and glycerine is that 396 parts by 
weight of CO, represent 276 parts of glycerine, or, in other words, the weight 
in grammes of CO, found multiplied by ‘69697 gives the amount of glycerine 
in the quantity weighed out for analysis. The process is conducted in an ordi- 
nary apparatus for the estimation of carbon dioxide, like that figured on page 148, 
fig. 36. The fluid containing the glycerine is first tested for the presence of 
sugars, both cane and glucose, and if they are absent a measured quantity 
(say 100 c.c.) is evaporated on the water bath with 3 c.c. of milk of lime and 
2 grammes of pure sand, till a fairly detachable residue is obtained. This is 
then scraped from the basin and extracted in the ‘‘Soxhlet” with absolute 
alcohol. The alcohol is distilled off in a weighed flask and the weight of the 
residue taken. The residue is then dissolved in a little distilled water, and 
such an aliquot part taken for analysis as shall not contain more than *5 gramme 
of glycerine. This is introduced into the apparatus with 4 grammes of potassium 
bichromate in saturated solution, and into the acid reservoir are placed ro c’c. 
of strong sulphuric acid, the absorbing tube being also charged with the same 
acid. The apparatus is weighed, and then the acid in the reservoir is allowed 
to mix with the glycerine and bichromate. Action sets in, and after standing 
for three hours in a warmplace, the whole is heated to gentle ebullition, cooled, 
and weighed. The loss of weight equals the CO, evolved, and this is then 


calculated to glycerine as above, and lastly corrected from the aliquot part to — 


the whole. In the presence of sugar the liquid must first be inverted by 
boiling with dilute hydrochloric acid (if cane sugar be present), and then 
evaporated with an excess of barium hydrate instead of lime. ‘This will 
either decompose the sugars, or render them insoluble in the alcohol subse- 
quently applied. 


DIVISION II. ANALYSIS OF URINE. 


A sample of urine taken for analysis should be the first passed by the 
patient in the morning, or, better, a portion taken from the total twenty-four 
hours’ urine. 

The following are the chief points on which information is usually required 
by the physician who submits urine for examination to an analyst :— 


1. Take the specific gravity, which should range from 1°o15 to 1°025 at 60° F. 
For every 1° F. above 60° add ‘ooo1 to the observed specific gravity. By 
multiplying the last two decimals of specific gravity by 2°33 we have the 
grammes per litre of total solid matter. Make a note also of the daily 
quantity, which should be 1200 to 1500 c.c. (40—50 fl. oz.). On standing some 
time urine undergoes alkaline fermentation, and is alkaline in reaction. 


_ WNote.—In diabetes the gravity is too high, sometimes reaching 1'060, while in albuminur 
it is abnormally low, even occasionally falling to 1'005. 


2. Examine the reaction, which should be very faintly acid. 


a 


ANALYSIS OF URINE. 185, 


Ah EEE —_—EE— eee canna 


3. Set a portion to settle in a long glass, and examine the deposit under 
the microscope for calcium oxalate or phosphate, uric acid or urates, pus, 
casts of kidney tubes, etc., etc. (see pages 186-87). 


Note.—The nature of the deposit may also be confirmed chemically as follows :— 


(z) Warm the urine containing the sediment, when, if the latter should dissolve, it 
consists entirely of urates. In this case let it once more crystallise out, and. 
examine it by the ordinary course for Ca, Na, and NH,, to ascertain the 
bases. 


(4) If the deposit be not dissolved by heating, let it settle, wash once by decantation 
with cold water, and warm with acetic acid. Phosphates will dissolve, and 
may be reprecipitated from the solution by excess of NH,HO filtered out, 
well washed with boiling H,O, dissolved in HC,H,O,, and examined for Ca 
or Mg by the usual course for these metals in presence of PO, 


(c) If the deposit be insoluble in acetic acid, warm it with HCl. Any soluble 
portion is calcium oxalate, which may be precipitated by NH,HO. 


(d@) If the deposit be insoluble in HCl it is probably uric acid. In this case apply 
the murexid test as follows. Place it in a small white dish, remove moisture 
by means of a piece of bibulous paper, add a drop or two of strong HNO, 
and evaporate to dryness at a gentle heat. When cold add a drop of 
acy which will produce a purple color, deepened to violet by a drop 
of KHO. 


4. Test for albumin, as follows :— 


(a) Boiling test,—Filter the urine, place Io c.c. in a narrow test-tube, 
and add one drop of acetic or nitric acid. Heat the tube 
over a small flame in such a way that the ufper portion of 
the liquid only shall be heated. Coagulation will take place, 
and the presence of albumin will be evident from the formation 
of a turbidity ranging from a faint cloud to a dense coagulum, 
but always strongly contrasted with the clear liquid beneath, 
which was not heated. Mucin also precipitates with this test. 


(0) Nitric test—To five volumes of cold saturated solution of magnesium 
sulphate add one volume of nitric acid (sp. gr. 1°42), and pre- 
serve this reagent for use. Pour some perfectly clear filtered 
urine into a tube, and carefully add an equal volume of the 
reagent, delivered gently from a pipette so that the liquids shall 
not mix. An opalescent zone will form at the point of contact 
either immediately or within twenty minutes, according to the 
quantity of albumin present. ‘This zone should not dissolve on 
gently warming, but should be a distinct ring at the bottom of 
the urine, and not a general haze near the top, which latter 
indicates mucin. If the zone of contact has a pink color, 
indican or other coloring matter is excessive. Indican may 
be further confirmed by mixing equal volumes of urine, strong 
HCl, and chlorine water, which produces a violet color, and 
may be estimated by color titration with chloroformic solution 
of indigo of known strength. 


(c) Picric acid test.—Dissolve 7°5 grammes of pure crystallised trinitro- 
phenol (picric acid) in 500 c.c. of water, let it stand for some 
days to perfectly clarify, pour off, and preserve the reagent for 
use. Mix some of the filtered urine in a tube with an equal 
volume of this reagent, look for any cloud or precipitate, and 
then heat to boiling. The true albumin cloud will remain per- 
manent, while that due to peptones or alkaloids accidentally 


186 ANALYSIS OF URINE, ETC. 











A : é z 
= 2 ‘ C— Sarccuc. naleet 
Boog Foslale” Nr a“ Geeudt kL, (Caabsles } | 

De AMAaLG posed i 





: *% ‘ oe ° 
Like Prgacirns Cortetiroine tr, Cater, 


Wary Catt 
Fig. 46. 





ANALYSIS OF URINE. 187 








188 ANALYSIS OF URINE, ETC. 





present will be dissolved. Picric acid does not precipitate 
mucin, and is therefore a valuable confirmation test. 


(d) Bodekers method.—Take a drachm of the urine, acidulate it with 
acetic acid, and add some potassium ferrocyanide drop by drop 
till a clear excess has been added. If during the addition a 
precipitate forms, albumin is to be suspected. Mere traces 
require some time to cause the cloud. 


(e) Zo estimate the Albumin.—This may be done empirically by means 
of an albuminimetre (fig. 47). Fill to u with the 
urine and Rr with the precipitant (picric acid Io 
grammes, citric acid 20 grammes, and water to make 
1,000 c.c.). Mix by inverting the tube several 
times, not by agitation, and set aside for 24 hours. | 
The height of the precipitate, as indicated by the 
graduations, represents the grains of albumin per 
thousand c.c. of urine. Be careful to read the 
height of the precipitate from the middle of ‘the 
albuminous surface. If the urine is alkaline, make 
it acid with acetic acid. In the absence of such 
a convenient appliance we may take a weighed 
quantity of the urine, and allow it to drop into 
boiling water acidulated with acetic acid. Collect 
the precipitate on a tared filter, wash with boiling 
water, dry at 212°, weigh, and deduct the weight 
of the filter, when the balance = albumin in the 
weight of urine operated upon. 





























5. Test for grape sugar, as follows :— 


(a) Moore’s test.—Acidulate with acetic acid, boil, and 
filter out any albumin if necessary. Then mix the 
filtrate with equal parts of Zguor potasse and heat 
to boiling, when ordinary urine will turn brownish- 
red; but saccharine urine will become dark brown 
or black. 


(6) Boettger’s test (modified by Nylander).—Dissolve 
2° grammes of pure bismuth oxynitrate (free 
especially from silver) and 4 grammes of Rochelle 
salt in 100 grammes of 8 per cent. solution of 
sodium hydrate, and preserve for use. To use this 
reagent 1 c.c. of urine is added to ro c.c., and the 
whole boiled gently for some time, when if even 

only traces of sugar be present the mixture becomes black. 























(c) Fehling’s test.—Render the urine alkaline with potassium hydrate, 
and filter to remove any phosphates, etc., which may precipitate. 
Boil the filtrate with Fehling’s solution of copper (see page 121), 
and if a red precipitate should form, sugar is present. 


(d) To estimate the sugar.—This is best done by taking ro grammes of 
the urine and diluting it with water to 100 c.c. Place this 
solution into a burette, and run it gradually into ro c.c. of 
Pavy’s or Fehling’s solution, kept boiling in a flask as directed 
under the Volumetric Analysis of Sugar, page 121. The 
number of c.c. of urine used will contain *oo5 *gramme of grape 


ANALYSIS OF URINE. 189 


sugar if Pavy’s solution, or ‘o5 gramme if Fehling’s was used, 
machen oOo 100 X *O5 

c. used c.c. used 
the ro grammes of urine taken. 


(Pavy) or (Fehling) = sugar in 


(e) Estimation of sugar by fermentation.—Take one gramme of commer- 
cial compressed yeast (or 51, of a cake of Fleischmann’s Yeast), 
shake thoroughly in the graduated test-tube with 10 c.c. of 
the urine to be examined. Then pour the sal 
mixture into the bulb of the saccharo- 
meter. By inclining the apparatus the 
mixture will easily flow into the cylinder, 
thereby forcing out the air. Owing to the 
atmospheric pressure the fluid does not 
flow back, but remains there. The ap- 
paratus is to be left undisturbed for 20 to 
24 hours in a room of ordinary tempera- 
ture. If the urine contains sugar, alcoholic 
fermentation begins in about 20 to 30 
minutes. The evolved carbonic acid gas 

* gathers at the top of the cylinder, forcing the fluid back into 
the bulb. On the following day the upper part of the cylinder 
is filled with carbonic acid gas. The changed level of the 
fluid in the cylinder shows that the reaction has taken place, 
and indicates by the numbers—to which it corresponds— 
the approximate quantity of sugar present. If the urine con- 
tains more than 1 per cent. of sugar, then it must be diluted 
with water before being tested. Diabetic urines of straw 
color and a specific gravity of 1018—1022 may be diluted twice ; 
of 10221028, five times ; 1028—1038, ten times. The original 
(not diluted) urine contains, in proportion to the dilution, two, 
five, or ten times more sugar than the diluted urine. 





6. Test for bile, as follows :— 


(a) Oliver's test.—Dissolve 2 grammes of flesh peptone, ‘25 gramme 
of salicylic acid, and 2 c.c. of 33 per cent. acetic acid, in 
enough water to yield 200 c.c. of product. The solution 
should be rendered perfectly brilliant by passing it through 
frozen filtering paper. The urine, which should be very clear, 
is diluted to a specific gravity of 1008. One cubic centimetre 
of this is added to 3 c.c. of Oliver’s reagent. An opalescence 
at once appears, which will be found to be more or less distinct 
according to the quantity of bile salts present. Keller’s contact 
method can be advantageously employed for applying the test. 


(6) Gmelin’s test for bile pigments.—Place a drachm of nitric acid in a 
test-tube, and cautiously pour upon it an equal volume of the 
urine. In the presence of bile a play of colors from green to 
violet, blue, and red will be observed where the liquids touch. 


(c) Pettenkofer’s test for biliary acids.—Mix equal parts of urine and 
sulphuric acid, add one drop of saturated syrup, and apply a 
gentle heat. If biliary acids be present, the color will change 
from cherry-red to deep purple. 


Note.—Bilious urine is usually of a brownish-green color. 


190 ANALYSIS OF URINE, EITC. 





7. Test for urea, as follows :— 


(a) Separate any albumin (as directed in Moore’s test) if necessary, 
and evaporate an ounce of the urine to a syrupy consistence on 
the water bath. When cold add nitric acid, drop by drop, till 
crystals of nitrate of urea cease to deposit. 


(0) Estimation of urea.—This is performed by the hypobromite pro- 
cess already given at page 127. Normal urine contains 2 to 3 
per cent. 


8. Test for uric acid by mixing one ounce of the urine with one drachm 
of hydrochloric acid in a beaker, and set aside for some hours. The uric acid 
will be deposited in reddish-brown crystals, which may, if desired, be weighed 





Fig. 50.—Extraneous Matters often seen in Urine. 
A, silk; B, cotton; c, wool; D, linen; £, feather; F, mycelium; G, cork. 


and proved by the murexid test. Normal urine contains 3 to 7 parts per 
thousand. 

A volumetric method is also used which is based on the known fact 
that argentic urate is insoluble in ammonia, but dissolves in nitric acid. 
The solutions required are:—1. ‘=, ammonium-thiocyanate ;” dissolve . 
about 8 grammes of ammonium-thiocyanate in a litre of water, and check with 
X, argentic-nitrate solution ; dilute it for use with nine volumes of water. 
2. Dissolve 5 grammes of argentic nitrate in 100 c.c. of distilled water, 
and add ammonia until the solution becomes clear. 3. Dilute 70 per cent. 
nitric acid with two volumes of distilled water, boil, to destroy the lower 
oxides of. nitrogen, and preserve from the action of light. 4. A saturated 
solution of ferric alum. 5. Strong solution of ammonia. The following is a 
description of the process :—Place 25 c.c. of urine in a beaker with 1 gramme 
of sodium bicarbonate. Add 2 or 3 c.c. of strong ammonia, and then 
1 or 2 c.c. (or an excess) of the ammoniated silver solution. A special 
procedure is necessary in order to collect the precipitate, as follows :—Fill a 
glass funnel to about one-third with broken glass, and cover this with a 
bed of good asbestos to about a quarter of an inch deep. This is best done 


ANALYSIS OF URINE. 191 





by shaking the latter in a flask with water until the fibres are thoroughly 
separated, and then pouring the emulsion so prepared in separate portions on 
to the broken glass. On account of the nature of the precipitate and of the 
filter, it is necessary to use a Bunsen water pump in order to suck the liquid 
through. Having thus collected the precipitate, wash it with distilled water 
until the filtrate ceases to become opalescent with a solution of NaCl. Now 
dissolve the precipitate by washing it through the filter into a beaker, with 
a few cubic centimetres of the special nitric acid. Estimate the silver by 
Volhard’s method thus: Add to the liquid in the beaker a few drops of the 
ferric alum solution to act as an indicator, and from a burette carefully drop 
in +¢9 Ammonium thiocyanate solution until a permanent red color appears. 
The number of c.c. used, multiplied by 0'00168, gives the amount of uric acid 
in the 25 c.c. of urine. One milligramme may be added to this amount as an 
allowance for average loss, and the whole multiplied by 4 gives the percentage 
of uric acid in the urine. The sodium bicarbonate is added in the early part 
of the process, to prevent decomposition of the argentic urate, which would 
otherwise occur. 


g. Test for phosphates, as follows :— 


(a2) Add to one ounce of the urine a slight excess of ammonium 
hydrate, and boil. Ca3(PO,), and MgNH,PO, will both be 
precipitated, and the precipitate, if more than a distinct cloud, 
should be filtered out, dissolved in HCl, and analysed by the 
ordinary process already given for phosphates. 


(2) After filtering out the earthy phosphates as above, alkaline phos” 
phates may be tested for by adding magnesia mixture to the 
filtrate, and getting the usual precipitate of MgNH,PO, after 
standing some hours in a cold place. 


(c) Estimation of Phosphates.—This is done by the volumetric process 
with uranic nitrate, already described at page 123. Normal 
urine contains 2 to 3 parts P,O; per thousand. 


1o. Test for sulphates, as follows :— 


Acidulate a weighed quantity of the urine with HCl, warm, and add 
excess of BaCl,. If the precipitate appear too copious, estimate 
as usual, using 50 c.c. urine (see page 124). Normal urine 
contains 1°5 to 3 parts SO3 per thousand. 


11. Test for chlorides, as follows :— 


Acidulate a little of the urine with HNOs3 and add excess of argentic 
nitrate. If the precipitate thus produced looks very large, a 
weighed quantity of the urine should be taken, and the 
chlorides estimated by Volhard’s method (see page 116). 
Normal urine contains 5 to 1o parts sodium chloride per 
thousand. 


12. &lood is best seen under the microscope ; but urine containing it has 
always a very characteristic smoky appearance. A test for blood is to add 
tincture of guaiacum and ethereal solution of hydrogen peroxide, which pro- 
duce a sapphire blue ; but such color of itself should not be taken as positive 
proof without the blood discs being also visible under the microscope. 


192 ANALYSIS OF URINARY CALCULI. 
ee ee 
DIVISION III. ANALYSIS OF URINARY CALCULI. 


The following table will show at a glance the compositions and methods of 
proving the various calculi. 


1. Calculi, fragments of which, heated to redness on platinum, 
entirely burn away. 


NAME. 





Uric acid, C;N,H,O3 


Ammonium urate 


Cystine, C;H,;NSO, 


Xanthin, C;H,N,O, 


PuysICAL CHARACTERS. 





Brownish-red ; smooth 


or tuberculated ; 
concentric laminz 
(common) 


Clay-colored ; usually 
smooth, and rarely 
with fine concentric 
laminz (uncommon) 

Brownish-yellow, 
semi-transparent and 
crystalline (very 
uncommon) 


Pale polished brown 
surface (very 
common) 


un- 


Sa ee eg ee bc 


CHEMICAL CHARACTERS. 


——_———_—_——————— 


Insoluble in water; soluble in KHO 
by heat, but evolves no NH3;; dis- 
solves with effervescence in HNO,, 
and the residue on evaporating the 
solution is red and gives the murexid 
test. 

Soluble in hot water ; 
heated KHO, evolving NH. 
haves with HNO, like uric acid. 


soluble in 
Be- 


Insoluble in H,O, alcohol, and ether. 
Soluble in NH,HO, and depositing, 
when allowed to evaporate spon- 
taneously, hexagonal plates. When 
heated, gives off odor of CS). 

Soluble in KHO; soluble in HNO, 
without effervescence, and the solu- 
tion leaves on evaporation a deep- 
yellow residue. 


pM ee eee 
2. Calculi, fragments of which, heated to redness on platinum, 
do not burn away. 


hE 











NAME. PuyYSICAL CHARACTERS. CHEMICAL CHARACTERS. 
a i se 
Calcium oxalate, | Deep brown, hard, and | Insoluble in acetic acid, but soluble 
mulberry calculus, rough; thick layers without effervescence in HCl; 
CaCO, (common) heated to redness, it is converted 


Tricalcium phosphate, 
bone-earth calculus, 
Caz(PO,)» 


Magnesium ammonium 


phosphate, triple 
phosphate calculus, 
MgNH,PO, 


Mixed phosphates of 


Ca, Mg, and NH,, | 


fusible calculus 


Pale brown, with regu- 
lar laminze (uncom- 
mon) 


White, brittle, crys- 
talline, with an un- 
even and not usually 
laminated — surface 
(uncommon) 

White, and 

laminated 


rarely 


into CaCOs3, which dissolves with 
effervescence in acetic acid, and the 
solution gives a white precipitate 
with (NH,),C,O,. Heated strongly 
before the blowpipe, CaO remains, 
which, when moistened, is alkaline 
to test-paper. 

Infusible before the blowpipe, and 
residue, when moistened, is not al- 
kaline. Soluble in HCl, and the 
solution gives a gelatinous precipi- 
tate with excess of NH,HO. 

Fusible with difficulty before the 
blowpipe, evolving NH, and_re- 
sidue not alkaline. Soluble in HCl, 
and solution gives white cxystalline 
precipitate with NH,HO. 

Readily fusible before the blowpipe. 
Soluble in acetic acid,-and solution 
gives a white precipitate with 
(NH,),C,O, and the filtrate from 
that precipitate gives a white pre- 
cipitate with excess of NH,HO. 


ANALYSIS OF URINARY CALCULI. 193 


Process :—Heat to redness on platinum. 


Uric acid—no odor of NH; when boiled with 


KHO. 
Sty see ae Ae MEETS y' Sodium, urateodor of NE, when boiled with 

Bae. KHO 

Apply murexid test : 


Cystine—confirm. . 
- mes Bot answer Xanthine—confirm. 
issolve original calculus in 
2. Residue | HCl and add excess i on {lantaa Neyppt Pag = Phosphate. 


sodium acetate. Ppt. H,HO. A ppt. 


The results may be recorded as follows :— 


Analysis of Urine. 


a RMR cian, cs Gan uss schcaawsceceeddaesviotecees esata See aE Aes ee thatan aban euanger one 


PURGING TD YVSICIAD Hic, f.440.-sceces eso actestsc Be, ERE oo otk eee CE EL ate BETS as sno cectees cosine 

ANALYSIS, 

Physical Characters. 
DORM ERIA ACY ruth hss 9555s 04G4sh->b086K4sbedeeetss Spécificre cavity ie v-tow-se. ids Slcanvevachha lanka “ 
CRANES. S90 ree deb URT Go 05 wokevdvasbecesiscecse’s (SONSISLETIO® Pav ten caititet sans dete e dies lees tegkeceae 
Po See See eee 8 Ss er ge aay SPP tt eR eS 42 
See ROE 2 OER oat scapular sate once inane ds ReeactiOte.gh-.tdenawynws adtasd RO cs 
Normal Substances. 
ree BO eek Orr 0) reo Bhosphatés (3S. cele, SAG cglieooreaess 
Cs cory dha keen ate ante er RN ee Jes We > ah phate ene creaetapbet liters: fcwmrt ry. 
eats cae thas no- yadanen nen teeie SSL RECS hones soateat chrenths- an peated uasoaee rp eects 
Abnormal Matters in Solution. 

P(e aie SR ie Fe setasceweese Miuciy PRR. Gerad tase vein toxk fens 
Titith v net Rectal ide lea ne ei oeeee Glew upticcciet ee pete aaa 
a Oo ota masa 0si0is Go. du-o)fini tel. cihata ees suc owed ve vearad epentiag ge gudues «faseiaeariryr se 

Sediment, 
Wee eh Ae ces Sn de oe Ea Epithelitam s2. sitesscisescescaccasccvecssscsecveesee 
RE EEE ete steric acs vecenaysiescenacescee> os peeps eS ep Se ER Sg RT, oN ROE, 88 
TN Ta te shn ass esinve aren iets do cnsasese= Kuss Dui cg olas «ghee vb ead bs ce soca dal sone 
SY TN es Caf ls Eads okienenapaccse | Ut ocdeacsdeecobucka sdeddeskbeve' doves tg ucoae sa cteastatevayee 

Remarks, 

13 


CHA PEE Roce 


THE ANALYSIS OF GASES, POLARISATION, AND 
SPECTRUM ANALYSTS. 


DIVISION I. THE ANALYSIS OF GASES. 


THIS operation is conducted by measuring a volume of the mixed gas under 
definite conditions of temperature and pressure, then exposing it to the action 
of some substance having the power of absorbing some one constituent of the 
mixture, and again measuring the gas left. By seeing that the inside of the 
measuring tube is always kept moist the question of tension of aqueous vapor 
is equalised all through the experiment, and as many absorbents as may be 
necessary are employed in turn. Many of the gas-measuring appliances are 
large, costly, and require to be kept in special rooms devoted to the 
purpose. Quite recently, however, an American chemist, Mr. Keiser, has 
devised a gas-measuring apparatus which is likely, in the author’s opinion, to 
supersede all others for absorption analyses, because it is compact in form, 
may be easily carried about and used at any place, and yet is capable of 
measuring gas volumes with great accuracy. Long graduated glass tubes and 
graduated vessels of all kinds are discarded, and an instrument is constructed 
upon the principle of determining the volume of a gas from the weight of 
mercury which it displaces at a known temperature and pressure. From the 
weight of mercury displaced the volume of the gas can be determined with 
much greater accuracy than by a direct reading on a graduated glass 
eudiometer. 

The accompanying cut shows the construction of the measuring apparatus 
and the absorption pipette. a is the measuring apparatus, B is the absorption 
pipette; @ and 6 are glass bulbs of about 150 c.c. capacity. They are 
connected at the bottom by a glass tube of 1 m.m. bore, carrying the three- 
way stopcock d. The construction of the key of the stopcock is shown in 
the margin. One hole is drilled straight through the key, and by means of 
this the vessels a and 6 may be made to communicate. Another opening 
is drilled at right angles to the first, which communicates with an opening 
extending through the handle, but does not communicate with the first 
opening. By means of this, mercury contained in either a@ or 6 may be 
allowed to flow out through the handle ¢@ into'a cup placed beneath. The 
bulb 4 is contracted at the top to an opening 20 m.m. in diameter. ‘This is 
closed by a rubber stopper carrying a bent glass tube, to which is attached the 
rubber pump e. Toa second glass tube passing through the stopper a short 
piece of rubber tubing with a pinchcock is attached. By means of the pump e 
air may be forced into or withdrawn from 4, as one or the other end of the 
pump is attached to the glass tube. The bulb @ terminates at the top in a 
narrow glass tube, to which is fused the three-way stopcock « The construc- 


ANALYSIS OF GASES. 195 





tion of the key of this stopcock is also shown in the cut. By means of it the 
vessel a may be allowed to communicate with the outside air, or with the tube 
passing to the absorption pipette, or with the gauge g. The gauge ¢ is a glass 
tube having a bore 1 m.m. in diameter, and bent as shown in the figure. By 
pouring a few drops of water into the open end of this tube a column of water 
several centimetres high in both limbs of the tube is obtained. This serves 
as a manometer, and enables the operator to know when the pressure of the 
gas equals the atmospheric pressure. To secure a uniform temperature, the 
bulbs @ and @ are surrounded by water contained in a glass vessel. This 
vessel for holding water is merely an inverted bottle of clear glass from which 
the bottom has been removed. ‘The handle of the stopcock d passes through 
a rubber stopper in the neck of the bottle. A thermometer graduated to - 
is placed in the water near the bulb a. The whole apparatus is supported 
upon a vertical wooden stand. 

The absorption pipette B consists of two nearly spherical glass bulbs of 
about 300 c.c. capacity. They communicate at the bottom by means of a 
glass tube, 3 m.m. inside diameter. ¢ is a two-way stopcock. The holes in 
the key are drilled at right angles, so that the tube which connects with the 





Fig. 51. 


measuring apparatus may be put in communication either with the funnel or 
with the absorption bulb. The funnel is of service in removing air from the 
tube which connects the measuring apparatus with the absorption pipette. By 
pouring mercury or water into the funnel and turning the stopcocks ¢’ and ¢ in 
the proper directions all the air is readily removed. fis a rubber pump used 
in transferring gas from B to A. The lower part of the pipette contains 
mercury, which protects the reagent from the action of the air. 

To measure the volume of a gas, the vessel a is filled completely with pure 
mercury. This is easily accomplished by pouring the mercury into 4, and then, 
after turning ¢ until a communicates with the outside air, forcing it into a by 
means of the pump e. Any excess of mercury in @ is then allowed to flow out 
through the stopcock d. When a and @ are now placed into communication 
the mercury will flow from @ to 4, and gas will be drawn in through the stop- 
cock ¢c. The volume of mercury which flows into 4 is equal to the volume of 
gas drawn into a. When the mercury no longer rises in J and it is desired to 
draw in still more gas into a, then it is only necessary to exhaust the air in 4 
by means of the pump e. After the desired quantity of gas has been drawn 
into a the stopcock ¢ is closed. After standing a few minutes the tempera- 


196 ANALYSIS CR GASZS, POLARISATION, LI 





ture of the gas becomes the same as that of the water surrounding a. The 
pressure of the gas is then made approximately equal to atmospheric pressure 
by allowing the mercury to flow out of 4 into a weighed beaker placed beneath 
the stopcock @ until it stands at nearly the same level in both a and 4. 
Communication is now established between a and g, and by means of the 
pump e the pressure can be adjusted with the utmost delicacy until it is 
exactly equal to atmospheric pressure. ‘The stopcock d is then closed, and 
the remainder of the mercury in 4 is allowed to flow out into the beaker. The 
weight of the mercury displaced by-the gas divided by the specific gravity of 
mercury at the observed temperature gives the volume of the gas in cubic 
centimetres. 

If it is desired to remove any constituent of the gas by absorption, a pipette, 
B, containing the appropriate reagent, is attached to the measuring apparatus. 
All the air in the connecting tube is expelled by pouring mercury into the 
funnel, and turning the stopcocks ¢’ and cso that the mercury flows out through 
c. A little more than enough mercury to expel the gas in the vessel a is 
poured into 6. The small quantity of air which is confined in the tube con- 
necting 4 with the stopcock is removed by allowing a few drops of mercury to 
run out through 4. Then a@and 4 are placed in communication. ‘The stop- 
cocks ¢’ and ¢ are turned so that the gas may pass into the pipette, the 
mercury which filled the connecting tube passes into the absorbing reagent, 
and unites with that which is already at the bottom of the pipette. The 
transfer is facilitated by the pump e. After absorption the residual volume is — 
measured in the same way that the original volume was measured. @ is com- 
pletely filled with mercury from the upper to the lower stopcock, and all the 
mercury in 2 is allowed to run out; the gas is then drawn back into the 
measuring apparatus, the last portion remaining in the connecting tube being 
displaced by means of mercury from the funnel. The volume is then deter- 
mined as before. 

The calculation of the results of an analysis is very simple. If the tempera- 
ture and pressure remain the same during an analysis, as is frequently the 
case, then the weights of mercury obtained are in direct proportion to the 
gas volumes, and the percentage composition is at once obtained by a simple 
proportion. | 

If the temperature and pressure are’ different when the measurements are 
made, it is necessary to reduce the volumes to o° and 760 m.m. The 
following formula is then used :— 


v= W (H—h) 
~ D (1 + *00367 x #) 760’ 
in which ; 
W = weight of mercury obtained (in grammes), 
D = specific gravity of mercury at 7°, 
¢# = temperature at which the gas is measured, 
HT = height of the barometer, 
# = tension of aqueous vapor, 


Vv’ = reduced gas volume (in cubic centimetres). 


« In all the measurements made with the apparatus the gas is saturated 
with aqueous vapor, because it comes in contact with the water in the 
manometer gs. 


The chief absorbents employed in gas analysis are as follows :— 


A. Strong solution of potassium hydrate absorbs HCl, HBr, HI, 
COz, SO,, and H,S. 
B. Crystallised sodium phosphate absorbs HCl, HBr, and HI. 


ANALYSIS BY CIRCULAR POLARISATION, ETC. 197 


eee nce anne 


C. 1 vol. of 25°/, solution of pyrogallic acid + 6 vols. 60°/, solution 
of KHO absorbs O, (after removal of any gas absorbed by 
KHO alone). 


D. Concentrated solution of cuprous chloride in dilute hydrochloric 
acid absorbs CO (after removal of CO, and O, with alkaline 
pyrogallate). 


E. A solution of sulphuric anhydride in strong sulphuric acidy..0r 
solution of bromine, absorbs C,H,, and the other gaseous 
hydrocarbons of the series C,H,,, and of Geclign a 


F. Absolute alcohol absorbs ‘certain of the paraffines, except marsh gas. 


G. Adding an excess of pure oxygen, and then absorbing with alkaline 
pyrogallate, will remove NO together with the excess of oxygen 
used. 


H. Hydrogen and nitrogen are left to be estimated by difference. 
They may be separated by passing the mixture into an eudio- 
meter, and adding excess of pure oxygen, measuring the total 
volume, and passing an electric spark. The hydrogen then 
forms water, and the gas being remeasured, 2 of the total loss 
in volume represents the H, present. The excess of O, having 


then been removed by alkaline pyrogallate, the remainder is N3. 


Full details of the analysis of gases, beyond the scope of the present work, 
will be found in Sutton’s “ Volumetric Analysis.” 


DIVISION II. ANALYSIS BY CIRCULAR POLARISATION. 
THE SACCHARIMETER. 


Crystals which do not belong to the regular system (notably calc-spar) 
possess the power of double refraction. ‘That is to say, when a ray of light 
falls upon them, it is divided into two rays, one of which follows the ordinary 
rule of refraction, while the other takes a totally different course ; and the two 
rays are called respectively the “ ordinary ” and the “extraordinary” ray. 
The most convenient polarising medium is what is called a “Nicol’s prism.” ~ 
It is composed of a crystal of calc-spar cut into two portions in the direction 
of its axis, and the two parts thus obtained cemented together with Canada 
balsam. When a beam of light enters the prism, it is doubly refracted by the 
first portion of the crystal, and the extraordinary ray only passes through the 
second portion to the eye of the observer; while the ordinary ray is com- 
pletely reflected away by the layer of Canada balsam, and so lost to view. 
When this extraordinary ray is examined it is found to possess peculiar 
properties, such as showing color in transparent bodies which are usually 
colorless. This is accounted for by believing that it has become polarised 
—z.e., that all its vibrations have been reduced to the same plane. If the 
polarised light thus obtained be examined by means of another Nicol’s prism, 
it will be found that when the two prisms are placed with the principal 
sections parallel to each other, the ray will pass freely ; but if the second 
prism, called the analyser, be then turned round so that its chief section is 
at right angles to that of the first, the polarised ray will in turn be entirely 
reflected from the layer of balsam, and no light will now reach the observer’s 
eye. This holds good so long as nothing intervenes between the two prisms ; 
but it has been found that certain bodies, such as quartz, possess the power, 
when interposed between the prisms, of giving a color instead of darkness, 
owing to their possessing the power of twisting the polarised ray from its 


198 ANALYSIS OF GASES, POLARISATION, ETC. 





original plane. Such substances are said to possess the power of circular 
polarisation, either in a “right-handed” or “left-handed” direction, accord- 
ing as it is necessary to turn the prism either to the right or left from its 
proper position to once more produce complete passage of the colorless 
polarised ray. The direction of the rotation is indicated by the use of arrows, 
thus: go. Cane sugar, grape sugar, dextrin, maltose, creasote, camphor, 
tartaric acid, cinchonine, castor oil, croton oil, and oil of lemons rotate the 
plane of the polarised ray to the right; while fruit, or invert-sugar, quinine, 
cinchonidine, turpentine, and many essential oils, morphine, etc., have a left- 
handed rotation. 

There are two varieties of quartz, known as right-handed and left-handed, 
one of which rotates the plane of polarisation to the right, and the other to 
the left. Ifa plate of quartz 1 millimetre thick be placed between the two 
‘ Nicols,” the ray of polarised light is rotated, and, instead of being colorless, 
is colored, changing to all the colors of the spectrum as the analyser is turned, 
until it once more becomes colorless, and the amount that the analyser has 
to be turned (registered by a pointer on the degrees of the circle) is the index 
of rotary polarisation possessed by the quartz either in a right- or left-handed 
direction. If the turning of the analyser be now continued, color will again 
show itself, but this time it will be the color complementary to that at first 
produced. ‘Thus, if we start with a plate of quartz showing red between the 
uncrossed prisms, and rotate, we shall find that when we have turned through 
an angle of 45°, we get no color, but after that we begin to get the com- 
plementary color green, which becomes most intense at the right angle of 90°, 
when the prisms are crossed. The polariscope as used for analysis is therefore 
essentially (a) a Nicol’s prism acting as a polariser, (4) a plate of quartz 
usually divided down the centre, the one side being right-handed and the 
other left, (c) a tube to contain the solution, (2) another “Nicol” capable of 
being rotated, and having a pointer acting on degrees of the circle on a scale, 
(¢) a telescope to focus the line between the two sides of the quartz. When 
the pointer is placed at zero, the tube filled with water, and the line focussed, 
no color is seen on either side of it, but if a solution, say of sugar, be intro- 
duced, then color appears on one side of the line according to the nature of 
the sugar, and then the distance through which the pointer has to be moved 
round the graduated circle to get both sides of the quartz colorless is the 
degree of rotary polarisation. In practice, monochromatic light from a sodium 
flame is employed, and this, destroying all color, causes a dark shadow instead 
of a color to appear when the instrument is used, so enabling color-blind 
persons to employ it without difficulty. To use the instrument we make a 
solution of the body to be examined of a definite percentage strength by dis- 
solving a certain number of grammes in 100 c.c. of a solvent. We then fill the 
tube, observe the degree of rotation produced, and from that we calculate 


the absolute angle of rotation for the sodium light (always expressed as [a]) as 
follows :— 


Let a=the observed angle, ¢ the strength in grammes per 100 c.c., and / the length of the 
tube used in decimetres ; then— 


If the absolute angle thus found coincides with that obtained from the same substance in a 


state of purity, then the article under examination is pure, but if not, then a simple percentage 
calculation gives the impurity. 


Thus the [a]p of pure cane sugar = 66'5. A sample examined as above gave an [2]p = 60'0. 


60 x I0 
Then : each = 90'2 per cent. of real sugar present in the sample. 


- 


SPECTRUM ANALYSIS. 199 


So ee eee 


DIVISION III. SPECTRUM ANALYSIS. 


When a ray of sunlight is allowed to pass through a prism, it is deflected 
and dispersed into a number of rays differing in their degree of refrangibility. 
When these rays, as they pass from the prism, are caused to fall upon a white 
surface, they are observed to have a marked difference in color. The image 
so produced is called a spectrum ; and ‘when sunlight is thus treated it. is 
found to give a spectrum consisting of the following colors: viz., violet, indigo, 
blue, green, yellow, orange, and red. The violet end of the spectrum, owing 
to its greater refrangibility, is always the nearer to the base or broad end of 
the prism. By this means of separating the rays of light we are able to ascertain 
the peculiar properties of each of the colors which go to compose it, and we 
find that the chemical activity of light resides chiefly in the most highly re- 
frangible rays just outside the violet end of the visible spectrum, which are 
called the actinic rays ; while, on the other hand, the heat transmitted by the 
sun is most felt at the opposite or red end of the spectrum. 

Further research demonstrated that if we substituted the light emitted from 
various bodies in a state of incandescence to the action of a prism, the image 
or spectrum produced varied in each case, and was, moreover, almost ‘cha- 
racteristic of the particular bodies employed. This discovery led to the 
invention of the spectroscope, which, in its simplest form, consists of a 
metallic diaphragm with a narrow slit, through which a ray of light from the 
burning body is allowed to pass and is condensed by a lens upon a prism 
of glass, or, better still, a triangular bottle of thin glass filled with disulphide 
of carbon. At the opposite side of the prism is a short telescope, so arranged 
that an observer, looking through it, sees the spectrum or image produced 
by the light after passing through the prism. ‘This telescope works upon a 
graduated scale, by which its position for viewing any particular line observed 
can be noted. 

When ordinary solar light is examined through the spectroscope, a number 
of dark lines are found crossing the image at certain fixed points. They are 
called “ Frauenhofer’s lines,” and their position is characteristic of sunlight. 
It has been proved that such lines are only formed when the source of light 
contains volatile substances, as we find that the light emitted by a non-volatile 
heated body gives a continuous image devoid of lines. If, for example, a 
platinum wire be heated to a high temperature in a Bunsen burner, and the 
light thus produced be examined, no lines will be visible ; but if the wire be 
now tipped with a fragment of sodium chloride, and once more ignited, a 
bright line will suddenly appear in the yellow of the spectrum, and in so 
dazzling a manner as to render the whole of the rest of the image almost 
invisible. In carrying out this system of analysis, therefore, it is only necessary 
to procure a perfectly clean piece of platinum wire, with one end bent into 
the form of a loop, and place a Bunsen gas burner in such a position that the 
rays from anything heated in it will pass into the spectroscope. The wire is 
then to be moistened with a little hydrochloric acid, and having been dipped 
in the substance to be examined, is to be held in the hottest portion of the 
Bunsen flame, and its spectrum simultaneously observed through the spectro- 
scope, noting carefully the color, number, and position on the scale of the 
bright lines produced. When thus examined, we find that potassium exhibits 
one bright line in the red, and one in the blue ; lithium, one bright line in the 
yellow, and one more brillaint in the red; strontium, one blue, one orange, 
and six red lines; barium, a number of lines chiefly green and yellow; cal- 
cium, three distinct bright yellow lines, one within green, and some broad but 


200 ANALYSIS OF GASES, POLARISATION, ETC. 
ee 


indistinct ones in the orange and red; and lastly, sodium the single bright 
yellow line already mentioned. 

The student must commence with the examination of pure salts, carefully 
noting for reference the position of the index of the telescope on the scale 
where each characteristic line is found. When it is desired to examine any 
mixture, the telescope index is brought to the required position and the sub- 
stance is examined: if the proper line is seen, then the element searched for 
is present ; if not, it is absent. If we examine ordinary light which has been 
made to pass through solutions of various colored bodies, we obtain dark 
bands analogous to the lines of Frauenhofer, These are called absorption 
spectra, and are very useful in the detection of soluble coloring-matters. A 
solution of blood, for example, shows characteristic bands in the green of the 
spectrum. All this is a matter of special study, and to go farther into it would 
be beyond the scope of this volume. 


DIVISION IV. MELTING POINTS. 


The accurate taking of the melting point is an important factor in testing 
the purity of many solid organic bodies, notably of fats and waxes. Many 
methods have been from time to time proposed, but the following will be 
found to be sufficiently good for all ordinary purposes, and is, moreover, the 
method officially adopted in the Pharmacopceia. 

A piece of narrow glass tube is softened in the gas flame and drawn out, so 
as to give it a long thin end with a capillary bore. The fat or wax is melted, 
and a little of it is sucked up into this capillary tube and allowed to solidify 
therein. The tube is then tied to a delicate thermometer so that its capillary 
end (having the semi-opaque column of solidified fat-inside) just rests against 
the bulb of the thermometer. Both are now supported perpendicularly in a 
beaker of water, and heat is gently applied to the same. The rise of the 
thermometer and the appearance of the tube of fat being both observed, the 
height of the former, at the moment when the column of fat becomes trans- 
parent, is noted as the melting point required. It is always useful to repeat 
the process three times and to take the average as the true melting point. 


Students desiring to go more deeply into this subject are referred to Allen’s 
“Commercial Organic Analysis.” 


A. 
Absorbents, 196. 
Absorption spectra, 200. 
Acetanilide, 88. 
Acetates, 47. 
Acetic, acid, 47. 
Acidimetry, 114. 
Acidulous radicals, Detection 
of, 29, 75; 
Gravimetric estimation of, 


144. 
Adeps lane, 89. 
Air bath, 133. 
Sanitary analysis, 165. 
Albumin, 185. 
Albuminoid ammonia, I61. 
Aloin, 89. 
Alcohol, estimation of in 
spirits, etc., 169. 
Tests for, 88. 
Table of percentages, 170. 
Alkalies, Organic salts of, esti- 
mation, I12. 
Alkaline course, 59. 
Carbonates, estimation, 
Ill. 

Hydrates, estimation, I Io. 
Alkaloidal strength of scale 
preparations, 182. 
Alkaloids, table of reactions, 97. 

Detection, 9I. 

Estimation, 124. 

Tests for, 97. 

Strength of extracts, 179. 
Aluminium, 20. 

Estimation, 141. 
Ammonia, 128. 

Albuminoid, 161. 
Ammonium, 27. 

Estimation, 143. 
Analysis— 

Bread, 169. 

Butter, 168. 

Colorimetric, 128. 

Colored sweets, 171. 

Drugs, 174. 

Food, 165. 

Gases, Keiser’s apparatus, 

194. 


EeNab sex, 
nla Be 


Analysis (contd. )— 
Gravimetric, 131. 
Milk, 165. 

Mineral (of water), 149. 
Mustard, 171. 
Nitrometer, by the, 125. 
Pepper, I7I. 
Polariscopic, 197. 
Qualitative, I. 
Quantitative, 98. 
Sanitary, of water, 158. 
% aa, att, 105. 
Scale preparations, 93. 
Spectrum, 199. 
Starch, 172. 
Ultimate organic, 152. 
Urine, 184. 
Urinary calculi, 192. 
Vinegar, 173. 
Volumetric, 107. 


Analytical factors, use of, 134. 


Anode, 7. 
Antifebrin, tests for, 88. 
Antimonic acid, 46. 
Antimony, 16. 
Estimation, 139. 
Antipyrin, tests for, 90. 
Apparatus, 109, 152. 
Arseniates, 45, 147. 
Arsenic, 15. 
Estimation, 139. 
Arsenic acid, 45. 
Arsenious acid, 44. 
Estimation, 117. 
Arsenites, 44. 


| Assay of— 


Cinchona bark, 176. 
Opium, 179. 
Ash, of filters, 132. 
»» », organic bodies, 134. 


De 


Barium, 24. 

Estimation, 141. 
Barks, cinchona assay, 176, 
Bath, steam, 5. 


Beer, strength of, 169. 
Benzoates, 51. 
Benzoic acid, 51. 
Bile (urine), 189. 
Bismuth, 14. 
Estimation, 137. 
Blood (urine), 190. 
Bodeker’s method, 186. 
Boettger’s test, 186. 
Boiling-point, 5. 
Borates, 37. 
Borax beads, 60. 
Boric acid, 37. 
Boyle’s law, 105. 
Bread, analysis, 169. 
Bromates, 31. 
Bromides, 30. 
Estimation, 144. 
Separation, 53. 
Bromine, 30. 
Estimation, 118. 
Bunsen burner, 9. 
Butter, analysis, 168. 


Cc 


Cadmium, 15. 
Estimation, 137. 


| Calcium, 25. 


Estimation, 141. 
Calculi, urinary, analysis, 192. 
Carbolates, 51. 
Carbolic acid, 51, 57. 
Carbon, 36. 

Estimation, 153. 
Carbonates, 36, 147. 

Alkaline, III. 

Soluble, 126. 
Carbonic acid, 36. 
Cathode, 7. 

Cerium, 20. 

Charcoal, use of, 8. 
Charles’s law, 104, 
Chemical processes, I. 
Chloral hydrate, 115. 

Tests for, 89. 
Chlorates, 30. 


202 


INDEX. 


i 


Chlorides, 29, 53. 
Estimation, 144, 191. 
With bromides, detection 


of, 53- 

With iodides, detection 
of, 53: 
Chlorine, 29. 

Available, estimation, 118. 

Estimation, 118, 157. 
Chloroform, tests for, 88. 
Chromates, 45. 

Chromic acid, 45. 
Chromium, 21. 

Estimation, 141. 
Chrysarobin, tests for, 89. 
Cinchona, assay, 176. 
Citrates, 50. 

Citric Acid, 50. 
Clarke’s process, 163. 
Cobalt, 23. 

Estimation, 139. 
Coefficients for analysis, 130. 
Coffee, analysis, 171. 
Colloids, 6. 

Colorimetric analysis, 128. 
Copper, 14. 

Estimation, 137. 

Standard solution, 121. 
Crucible, Rose’s, 5. 

Crum process, 159. 
Crystallisation, 5. 
Cupellation, 4. 
Cupreine, test for, 181. 
Cyanates, 41. 

Cyanic acid, 41. 
Cyanides, 40, 144. 
Cyanogen, 40. 
Cyanuric acid, 41. 


28 


Decantation, 3. 
Density, vapor, 105. 
Detection of— 
Alkaloids, 75, 91. 
Bromine, hydrobromic 
acid and bromides, 30. 
Bromides in presence of 
iodides, 53. 
Carbolic acid in presence 
of salicylic acid, 57. 
Chlorides in presence of 
bromides, 53. 
Chlorides in presence of 
iodides, 53. 
Chlorine, hydrochloric 
acid, and chlorides, 29. 
Cyanides in presence of 


56. 
Formate in presence of 
fixed organic acids, 56. 
Glucosides, etc., 95. 
Todate in an iodide, 54. 
Inorganic acids, 78. 


ferro-and ferri-cyanides, 


Detection of (contd.)— 
Metals, 10. 
In any simple salt, 61. 
In complex mixtures, 65. 
Nitrate in presence of 
iodide, 55. 
Nitric acid (free) in pre- 
sence of Nitrate, 55. 
Nitrite in presence of a 
nitrate, 55. 
Organic acids, 80. 
Phosphate in presence of 
calcium, barium, stron- 
tium, manganese, mag- 
nesium, 56. 
In presence ofiron, 56. 
Soluble sulphide in pre- 
sence of sulphite and 
sulphate, 54. 
Sugar, 75. 
Dialysis, 5. 
Distillation, 4. 
Dragendorff’s tables, 97. 
Drugs, analysis, 174. 
Resinous (strength of), 
181. 
Dumas’ process, 106. 













39 


fee 


Ebullition, 5. 

Elaterin, tests for, 89. 
Electrolysis, 6. 

Ether, Nitrous (estimation), 


125. 
Kthylsulphates, 47. 
Estimation of— 
Albumin, 186. 
Alkaline hydrates, 110. 
se carbonates, ITI. 
Alkaloids, 124. 
Aluminium, 141. 
Ammonia (Nesslerising), 
128. 
Ammonium, 143. 
Antimony, 139. 
Arseniates, 147. 
Arsenic, 139. 
Arsenious acid, 117. 
Ash, of filters, 132. 
» 95 Organic .. bodies, 
134. 
Barium, 141. 
Bismuth, 137. 
Bromides, 144. 
Bromine, 118. 
Cadmium, 137. 
Calcium, 141. 
Carbonates, 147. 
Carbon dioxide, 165. 
Carbon and hydrogen, 153. 
Chlorides, 144. 
Chlorine, 157. 
> free, 118. 
st available, 118. 


Estimation of (contd. )— 
Chromium, 141. 
Cobalt, 139. 
Copper, 137. 
» and iron, minute 
traces, 129. 
Extracts, alkaloidal 
strength of, 179. 
Fatty acids in soap, 183. 
Ferric and ferrous salts, 
120, 121, 
Glycerine, 183. 
Gold, 138. 
Gravimetric (of metals), 


135. 
Hydrocyanic acid, 116. 
Hydrogen peroxide, 127. 
Todides, 144. : 
In presence of bromide 
and chloride, 144. 
Todine, Free, 118. 
Iron, 140. 
Lead, 112, 135. 
Manganese, 140. 
Magnesium, 142. 
Mercury, 136. 
Moisture, 134. 
Nickel, 140. 
Nitrates, 145. 
Nitric acid in Nitrates, 
126. 
Nitrogen, 155. 
Nitrous Ether, 125. 
Oleic acid, 183. | 
Organic salts of alkalies, 
112, 
Oxalic acid, 148. 
Phenol, 182. 
Phosphates, 145. 
In artificial manures, 
146. 
Phosphoric acid, 123. 
Phosphorus, 157. 
Platinum, 138. 
Potassium, 142. 
Resinous drugs, 181. 
Silicic acid, 148. 
Silver, 135. 
Sodium, 142. 
11 one TLL COs 
Soluble carbonates, 126. 
»  haloid salts, 115. 
Sugar, 123, 189. 
Starch, 123, 172. 
Sulphates, 145. 
Sulphides, 144. 
Sulphur, 157. 
Sulphurous acid, 117. 
Tartaric acid, 148. 
Thiosulphates, 118. 
Tin, 138. 
Urea in urine, 127. 
Zinc, 140. 
Evaporation, 5. 
Examination, preliminary, 58. 
Extraction, 2. 
Extracts, alkaloidal strength 
of, 179. 





F. 


Factors, analytical (use of), 134. 
Fatty acids, estimation of, 183. 
Fehling’s solution, 121. 
Test in urine, 186. 
Ferric and ferrous salts, esti- 
mation, 120. 
Ferricyanides, 42. 
Ferro- from _ferri-cyanides, 
separation, 56. 
Ferrocyanides, 41. 
Filters, preparation of, 131. 
ash, estimation, 132. 
Filtration, 3. 
Flame-oxidising, 7. 
reducing, 7. 
tests, 60. 
Fluorides, 29. 
Food analysis, 165. 
Formic acid and formates, 46. 
Frauenhofer’s lines, 199. 
Fulminic acid, 41. 
Fusion, 4. 


G, 


Gallic acid, 52. 
Gases, sp. gr. 104. 

Analysis of, 194. 

Gaseous impurities (testing for, 
in air), 165. 

Gelatin, tests for, 89. 

Glucosides, 95. 

Glusidum, tests for, 89. 

Glycerine, 88, 183. 

Gmelin’s test, 189. 

Gold, 17. 

Estimation, 138. 
Gravill’s test, 127. 
Gravimetric estimation, 135. 

Acidulous radicals, 144. 

Metals, 135. 
Gravity, specific, 

urine, 184. 
Group reagents, IO. 


1003; of 


H. 


Haloid salts, 115. 
Hardness, Clark’s process, 163. 
Hydrates, 32. — 
Alkaline, estimation, 110. 
Sodium, 114. 
Hydriodic acid, 31. 
Hydrobromic acid, 30. 
Hydrochloric acid, 29. 
Hydrocyanic acid, 40, 116. 
Hydrofluoric acid, 29. 
Hydrofluosilicic acid, 38. 
Hydrogen, estimation, 153. 
Peroxide, estimation, 127. 
Hydrosulphuric acid, 33. 
Hypobromites, 31. 


INDEX. 


Hypochlorites, 30. 
Hypophosphites, 42. 
Hyposulphites, 34. 


ie 


Igniting precipitates, 133. 
Indicators, 107. 
Inorganic acid course, 78. 
Iodate with iodide, detection 
of, 54. 
Todates, 32. 
Iodoform, tests for, 89. 
Todides, 31, 55. 
Estimation, 144. 
Iodine, 31. 
Estimation, 118. 
Standard solution, 117. 
Iron, 18. 
Estimation, 140. 


J. 
Jalapin, tests for, 89. 


K. 


Keiser’s apparatus, 195. 
Kipp’s apparatus, 9. 
Kjeldahl’s process, 156. 


L. 


Lactates, 48. 
Lactie acid, 48. 
Lanolin, 89. 
Laws— 

Boyle’s, 105. 

Charles’s, 104. 
Lead, 12. 

Estimation, 112, 135. 
Liebig’s Condenser, 4. 
Lithium, 26. 
Lixiviation, 2. 


M. 


Magnesium, 26. 
Estimation, 142. 
Malates, 49, 57- 
Malic acid, 49. 
Manganates, 45. 
Manganese, 21. 
Estimation, 140. 
Manures, 
Estimation of phosphates 
_ in, 146. 
Mayer’s standard solution, 124. 
Measuring and weighing, 99. 
Meconates, 51. 


203 


Meconic acid, 51. 
Melting points, 200. 
Mercuricum, 13. 
Mercurosum, I2. 
Mercury, estimation, 136. 
Metals, detection of, 10. 
Gravimetric estimation, 
135; 
In complex mixtures, 65. 
Present in a simple salt, 
61. 
Separation into groups, 
10 ; (Hamilton) 64, 66. 
Tables for detection, 62. 
Metaphosphoric acid and salts, 


43- 

Method, Meyer’s, 105. 
Pavy’s, 122. 
Varrentrapp and Will, 


EY 
Volhard’s, 116. 
Methylated spirit, in tinctures, 
150-6 
Milk analysis, 165. 
Mineral analysis in water, 149. 
Moisture, estimation, 134. 
Moore’s test, 186. 
Murexid test, 185. 
Mustard analysis, 171. 


N. 


Nesslerising, 128. 
Nicol’s Prism, 197. 
Nickel, 23. 
Estimation, 140. 
Nitrates, 39, 55, 159. 
Nitric acid, 39. 
Nitric acid, estimation, 126, 
Nitrite with nitrate, detection 
of, 55. 
Nitrites, 38. 
Nitrogen, estimation, 155, 159. 
Nitrometer, use of, 
Analysis by, 125. 
Nitrous acid, 38. 
Nitrous ether, estimation, 125. 


O. 


Oleates, 48. 

Oleic acid, 48, 183. 

Oliver’s test, 189. 

Opium, assay, 179. 

Organic acid course, 80. 
Analysis, ultimate, 152. 
Matter in air, 165. 

Orthophosphoric acid, 43. 

Orthophosphates, 43. 

Oxalates, 48. 

Oxalic acid, 48, 148. 
Standard solution, 110. 

Oxidation, 7. 

Oxides, 33. 


204 


INDEX. 





ie 


Paraldehyd, tests for, 88. 
Pavy’s method, 122. 
Pepper analysis, 171. 
Perchlorates, 30. 
Periodates, 32. 
Permanganates, 45. 
Pettenkofer’s test, 189. 
Phenacetin, tests for, 90. 
Phenazone, tests for, 90. 
Phenol and Phenates, 51, 182. 
Phosphates, detection of, 43, 
56, 191. | 

Estimation, 145, 191. 
Phosphites, 43. 

Phosphoric acid, 43. 

Estimation, 123. 
Phosphorous acid, 43. 
Phosphorus, estimation, 157. 
Picrotoxin, tests for, 90. 
Platinum, 18. 

Estimation, 138. 
Podophyllin, tests for, go. 
Poisons in mixtures (testing 

for), 95. 
Polarisation, analysis by, 197. 
Potassium, 27. 
Bichromate, standard so- 
lution, 119. 

Estimation, 142. 
Precipitates, drying, etc., 132. 
Precipitation, 2 
Preliminary examination, 58. 
Process, Clark’s, 163. 

Crum’s, 159. 

Dumas’, 156. 

Kjeldahl’s, 156. 

Reichert’s, 168. 
Processes, chemical, I. 

Special analytical, $4. 
Pyrogallic acid, 52. 

Pyrology, 7. 
Pyrophosphoric acid and salts, 
43: 


Q. 


Qualitative analysis— 
Detection of metals, Io. 
Detection and separation 

of Acidulous Radicals, 

29.13 
Detection of 

salts, 58. 
Detection of Alkaloids, 

and of *‘Scale”’ medici- 

nal preparations, 9I. 
Processes, I. 

Quantitative analysis— 
Separations, 149. 

Specific gravity, 100. 
Standard solutions, 107. 
Vapour density, 105. 
Weighing and measuring, 


unknown 


9 
Quartz, 198. 
Quinine sulphate (testing), 181. 


R. 


Radicals, acidulous, 29, 75, 
144. 
Reagents, IO. 
Group L, 11. 
Group II. Div. A, 13. 
Group II. Div. B, 15. 
Group III. Div. A, 18, 
Group III. Div. B, 21. 
Group IV., 24. 
Group V., 26. 
Reduction, 7, 8. 
Reichert’s process, 168, 
Resin, tests for, 90, 95. 
Resinous drugs (strength of), 
181. 
Resorcin, tests for, 90. 


S. 


Saccharimeter, 197. 
Saccharine, tests for, 89. 
Salicylic acid, 52. 

Salts, detection of unknown, 


Estimation of ferrous and 
ferric, 120. 
Estimation of 
haloid, 115. 
Used in pharmacopceia,64. 
Sanitary analysis of air, 165. 
Sanitary analysis of water, 158. 
Santonin, tests for, go. 
Scale preparations, 93. 
Alkaloidal strength of, 
182. 
Separation— Group metals, 
66, 74. 
Arseniate from phosphate, 


soluble 


: Chlorates from chlorides, 


53- 
Chlorides, iodides, bro- 
mides from nitrates, 55. 
Cyanides from chlorides, 


Ferro- from ferri-cyanides, 


Iodide from bromide and 
chloride, 53. 

Metals into groups, 66. 

Oxalates, - tartrates, 
trates, malates, 57. 

Quantitative, 149. 

Silica from all other acids, 


ci- 


54: 
Sulphides, sulphites Hh 
sulphates, 54. 
Sulphonal, tests for, go. 
Thiosulphates, from sul- 
phides, 54. 
Silica, 37, 54. 
Silicates, 37. 
Silicic acid, 37, 148. 
Anhydride, separation of, 
54- 


Silver, II. 
Estimation, 135. 
Soap, fatty acids in, 183, 
Sodium, 27. 
Estimation, 142. 
Hydrate, Standard solu- 
tion, 114. 
Nitrite, estimation of, 126. 
Soil, estimation of phosphates 
in, 146. 
Solution, I 
Solutions, standard, 107. 
For testing acidulous 
radicals, 77. 
Separate (treatment of), 


174. 

Solubility tables, 82. 

Soxhlet’s apparatus, 2. 

Special processes, 84. 

Specific gravity, 100. 

Gases, 104. 

Liquids, 100. 

Practical application, 103. 
Solid bodies, 102. 

Urine, 184. 

Spectrum analysis, 199. 

Spirits, alcoholic strength, 169. 
Table for percentages, 

170. 

Standard Solutions— 
Argentic nitrate, I15. 
Barium chloride, 124. 
Copper, Fehling’s, 121. 
Iodine, 117. 

Mayer’s, for alkaloids, 
124. 

Oxalic acid, I10. 

Phosphate, 123. 

Potassium bichromate, 
119. 

Soap, 163. 

Sodium hydrate, 114. 

Sulphuric acid, 114. 

Thiocyanate, 117. 

Thiosulphate, 118. 

Standards of strength, vwzde 

standard solutions, as 
above. 

Stannates, 46. 

Stannic acid, 46. 

Starch estimation, 123, 172. 

Stearates, 48. . 

Stearic acid, 48. 

Strength of extracts (alka- 

loidal), 179. 
Resinous drugs, 180. 
Standards of, 113, 

etc. 

Strontium, 25. 

Sublimation, 4. 

Succinates, 49. 

Succinic acid, 49. 

Sugar estimation, 123. 

In urine, 186. 

Sulphates, 35, 91. 
Estimation, 145, 191. 

Sulphides, 33, 54. 
Estimation, I14. 


II5, 


Sulphides, sulphites, and sul- 
phates, separation of, 


54- 

Sulphites, 35, 

Sulphocyanates, 41. 

Sulphovinates, 47. 

Sulphur, 33. 

: Estimation, 157. 

Sulphuretted hydrogen, pre- 

paration of, 9, 

Sulphuric acid, 35. 

Sulphurous acid, 35. 
Estimation, 117. 

Sweets (coloured), analysis, 
17%. 

Sykes’s hydrometer, 101. 


a ie 


Tables-— 

Coefficients for analysis, 
130. 

Degrees of thermometer, 

~ 107. 

Detection of the metal in 
a simple salt, the metals 
as in pharmacopceia, 64. 

Detection of the metal in 
a solution containing 
one base only, 62. 

Distinction between gallic, 
tannic, and pyrogallic 
acids, 52. 


INDEX. 


Tables (contd.)— 
General reaction of alka- 
loids, 97. 
Milk, specific gravity of, 
167, 
Percentages 
170. 
Separation of metals into 
groups, 66. 
Solubility of salts, 82. 
Tannic acid, 52. 
Tartaric acid, 49, 148. 
Tartrates, 49. 
Testing for poisons, 95. 
Chief alkaloids, 96. 
Gaseous impurities, 165. 
Quinine sulphate, 181. 
Thiocyanates, 41. 
Thiosulphates, 34, 118. 
Tip, Y7. 
Estimation, 138. 
Tinctures— 
Alcoholic strength, 169. 
Methyl spirit in, 180. 
Toxicological analysis, 95. 


U. 


of alcohol, 


Ultimate organic analysis, 152. 
Urea, estimation, 127, 190, 
Uric acid, 190. 
Urinary calculi, analysis, 192. 
Urine, 127. 

Analysis, 184. 


205 


Valerianates, 47. 

Valerianic acid, 47. 

Van Babo’s apparatus, 9. 
Vaporisation, 5. 

Vapour, specific gravity, 104. 
Vapours, density of, 105. 
Varrentrapp & Will, 155. 
Vinegar analysis, 173. 

- Sulphuric acid in, 173. 
Volhard’s method, 116. 
Volumetric analysis, 107. 

Coefficients for, 130. 


W. 


Washing precipitates, 132. 
Water, 32. 
Mineral analysis of, 149. 
Sanitary analysis of, 158. 
Weighing, 98, 109. 
Precipitates, 133. 
Westphal balance, 102. 
Will & Varrentrapp, 155, 
Wines, alcoholic strength, 169. 


Z. 


Zinc, 22. 
Estimation, 140. 


Printed by Hazell, Watson, & Viney, Ld., London and Aylesbury. 






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ACTON. The Functions and Disorders of the Reproductive Organs in Childhood, 
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ALLEN, HARLAN, HARTE, VAN HARLINGEN. Local Therapeutics. 
A Handbook of Local Therapeutics, being a practical description of all those 
agents used in the local treatment of diseases of the Eye, Ear, Nose, Throat, 
Mouth, Skin, Vagina, Rectum, etc., such as Ointments, Plasters, Powders, 
Lotions, Inhalations, Suppositories, Bougies, Tampons, and the proper methods of 
preparing and applying them. By HARRISON ALLEN, M.D., Emeritus Professor 
of Physiology in the University of Penna. ; Laryngologist to the Rush Hospital 
for Consumption; late Surgeon to the Philadelphia and St. Joseph’s Hospitals. 
GEORGE C. HARLAN, M.D., late Professor of Diseases of the Eye in the Philadel- 
phia Polyclinic and College for Graduates in Medicine; Surgeon to the Wills 
Eye Hospital, and Eye and Ear Department of the Pennsylvania Hospital. 
Ricuarp H. HartTE, M.D., Surgeon to the Episcopal and St. Mary’s Hospital ; 
Ass’t Surg. University Hospital; Demonstrator of Osteology, University of Penn- 
sylvania; and ARTHUR VAN HARLINGEN, M.D., Professor of Diseases of the Skin 
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Clinical Lecturer on Dermatology in Jefferson Medical College ; Dermatologist to 
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ALLEN. Commercial Organic Analysis. A Treatise on the Modes of Assaying 
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ANDERSON. A Treatise on Skin Diseases. With special reference to Diagnosis 
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McCALL ANDERSON, M.D., Professor of Clinical Medicine, University of Glasgow. 
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ARCHIVES OF SURGERY. Edited by JonATHAN HUTCHINSON, F.R.S. Colored 
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ARLT. Diseases of the Eye. Clinical Studies on Diseases of the Eye. Including the 
Conjunctiva, Cornea and Sclerotic, Iris and Ciliary Body. By Dr. FERD. RITTER 
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by their appropriate tests, Hygiene, etc. By GEORGE ARMATAGE, M.R.C.V.S. 
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BALLOU. Veterinary Anatomy and Physiology. By Wm. R. BALLou, M.D., 
Prof. of Equine Anatomy, New York College of Veterinary Surgeons, Physician 
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BAR. Antiseptic Midwifery. The Principles of Antiseptic Methods Applied to 
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BARRETT. Dental Surgery for General Practitioners and Students of Medicine 


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BARTLEY. Medical and Pharmaceutical Chemistry. Third Edition. A Text- 
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BEALE. On Slight Ailments; their Nature and Treatment. By LIonEL S. BEALE, 
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How to Work with the Microscope. A Complete Manual of Microscopical 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 7 





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BLACK. Micro-Organisms. The Formation of Poisons. A Biological study of 
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CAIRD AND CATHCART. Surgical Handbook. For the Use of Students and 
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CAMERON. Oils and Varnishes. A Practical Handbook, by JAMES CAMERON, 
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CARPENTER. The Microscope and Its Revelations. By W. B. CARPENTER, 
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CAZEAUX and TARNIER’S Midwifery. With Appendix, by Mundé. The 
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perial Academy of Medicine, Adjunct Professor in the Faculty of Medicine in 
Paris. Remodeled and rearranged, with revisions and additions, by S. TARNIER, 
M.D. Eighth American, from the Eighth French and First Italian Edition. 
Edited by ROBERT J. HEss, M.D., Physician to the Northern Dispensary, Phila., 
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COBLENTZ. Manual of Pharmacy. A Text-Book for Students. By ViRGIL 
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MEDICAL AND SCIENTIFIC PUBLICATIONS. 9 





CLEVELAND'S Pocket Dictionary. A Pronouncing Medical Lexicon, containing 
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COLLIE, On Fevers. A Practical Treatise on Fevers, Their History, Etiology, 
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COPLIN and BEVAN. Practical Hygiene. By W. M. L. Coptiy, M.p., Adjunct 
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A Manual for Monthly Nurses. Third Edition. 32mo. Cloth, .50 

DALBY. Diseases and Injuries of the Ear. By Six Wittam B. Dacpy, M.D., 
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DAVIS. Biology. An Elementary Treatise. By J. R. AINSWORTH DaAvVIs, of 
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DAVIS. A Manual of Obstetrics. Being a complete manual for Physicians and 

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College, etc. Second Edition, Revised. With 16 Colored and other Lithograph 
Plates and 134 other Illustrations. 12mo. Cloth, $2.50 

Clinical Obstetrical Chart. Designed by Ep. P. DAVIS, M.D., and J. P. CROZER 
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DAVIS. Essentials of Materia Medica and Prescription Writing. By J. 
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FAGGE. The Principles and Practice of Medicine. By C. HILTON FaGGE, M.D., 
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FOWLER’S Dictionary of Practical Medicine. &y Various Writers. An Ency- 
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FULLERTON. Obstetrical Nursing. A Handbook for Nurses, Students and 
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Nursing in Abdominal Surgery and Diseases of Women. Comprising the 
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GARROD. On Rheumatism. A Treatise on Rheumatism and Rheumatic Arthritis. 
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GOODHART and STARR’S Diseases of Children. The Student’s Guide to the 
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GOULD. The Illustrated Dictionary of Medicine, Biology, and Allied Sciences. 
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The Medical Student’s Dictionary. Including all the Words and Phrases 
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to our readers, feeling sure that it will prove of much value to them.”—American Journal of 
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The Pocket Pronouncing Medical Lexicon. (12,000 Medical Words 
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*.* Sample pages and descriptive circular of Gould's Dictionaries sent free upon 
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This Visiting List is published in November of each year. 


P. BLAKISTON, SON & CO., PHILADELPHIA. 





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